Process for producing cellulose derivative and cellulose derivative

ABSTRACT

A process for producing a cellulose derivative, comprising: a first step including reacting a cellulose and a first reactant comprising a long-chain reactant for reacting with a hydroxy group of the cellulose to introduce a long-chain organic group having 5 or more carbon atoms, in a solid-liquid heterogeneous system, to form a cellulose derivative in a swollen state, the cellulose derivative having the long-chain organic group having 5 or more carbon atoms introduced therein and having a part of hydroxy groups of the cellulose remained, and performing solid-liquid separation to obtain the cellulose derivative as an intermediate; and a second step including reacting the intermediate cellulose derivative and a second reactant comprising a short-chain reactant for reacting with a remaining hydroxy group of the intermediate cellulose derivative to introduce a short-chain organic group having 4 or less carbon atoms to form a final cellulose derivative having the short-chain organic group having 4 or less carbon atoms introduced therein.

TECHNICAL FIELD

The present invention relates to a process for producing a cellulosederivative and the cellulose derivative.

BACKGROUND ART

Bioplastic using a plant as a raw material can contribute to acountermeasure against petroleum depletion and global warming and hasbeen started being used not only in common products such as packaging,containers and fibers but also in durable products such as electronicsand automobiles.

However, general bioplastics, such as polylactic acid,polyhydroxyalkanoate and modified starch, all use starch materials, moreprecisely, edible parts, as raw materials. Accordingly, for fear offuture food shortage, it has been desired to develop a novel bioplasticusing a non-edible part as a raw material.

As a raw material of a non-edible part, cellulose which is a maincomponent of wood and plant is representative, and various types ofbioplastics using the cellulose have been already developed andcommercialized.

However, since a step of chemically modifying cellulose to obtain aresin is complicated and laborious and much energy is required forproduction, manufacturing cost of a cellulose resin is high. Inaddition, since durability (strength, heat resistance, water resistance,etc.) of a produced resin is not sufficient, use of the resin islimited.

Cellulose is produced as pulp by chemically separating lignin andhemicellulose from wood, etc., with the help of a chemical agent. Incontrast, cotton can be used as it is since it is virtually formed ofcellulose. Such a cellulose, which is a high molecular weight compoundformed by polymerization of β-glucose, has a large number of hydroxygroups and thus has strong intermolecular force due to hydrogen bonds.Because of this, cellulose is hard and fragile, and has nothermoplasticity and a low solubility in a solvent except a specialsolvent. In addition, due to a large number of hydrophilic hydroxygroups, water absorbability is high and water resistance is low.

For improving such properties of a cellulose, various investigationshave been made.

As a method for improving the properties of a cellulose, a method ofsubstituting a hydrogen atom of a hydroxy group in a cellulose with ashort-chain acyl group such as an acetyl group is known. According tothis method, since the number of hydroxy groups can be reduced, theintermolecular force of a cellulose can be reduced. A furtherinvestigation has been made for producing a cellulose derivative havingsatisfactory thermoplasticity and water resistance by introducing along-chain organic group having a larger number of carbon atoms inaddition to a short-chain acyl group such as an acetyl group.

For example, Patent Literature 1 describes a cellulose derivativeproduced by substituting at least a part of hydrogen atoms of hydroxygroups of a cellulose with a short-chain acyl group (for example, analiphatic acyl group having 2 to 4 carbon atoms) and a long-chain acylgroup (for example, an aliphatic acyl group having 5 to 20 carbonatoms), and that the cellulose derivative has a low water absorptionrate, satisfactory thermoplasticity, strength and fracture elongationand is suitable for molding process.

Patent Literature 2 describes a cellulose derivative having cardanolintroduced therein, and that the cellulose derivative was improved inthermoplasticity, mechanical characteristics and water resistance.

Patent Literature 3 describes a cellulose derivative having cardanol andabietic acid introduced therein, and that the cellulose derivative wasimproved in thermoplasticity, mechanical characteristics and waterresistance.

CITATION LIST Patent Literature

Patent Literature 1: JP2010-121121A

Patent Literature 2: WO2011/043279

Patent Literature 3: WO2011/043280

SUMMARY OF INVENTION Technical Problem

Processes for producing a cellulose resin described in the above relatedart have a problem in that large energy load is required for a step ofrecovering a product. To explain more specifically, in these productionprocesses, the product, i.e., a cellulose derivative, is produced butdissolved in a reaction solution. Thus, the product is obtained throughsolid-liquid separation by adding a large amount of a poor solvent,which scarcely dissolves the product, to the reaction solution toprecipitate the product. Because of this, much energy is required forrecovering a solvent, a catalyst, a reactant or its derivative from alarge amount of reaction solution diluted with a poor solvent.

In the meantime, a cellulose is generally esterified with acetic acid bya process using a dissolving method, in which a product is dissolved ina solvent; however, it is known that the esterification can be alsoperformed by a process using a non-dissolving method, in which a productis not dissolved in the solvent. However, in this process, it ispossible to bind an acetyl group having a small number of carbon atomsbut it was difficult to bind a long-chain organic group having a largenumber of carbon atoms.

An object of the present invention is to provide a process for producinga cellulose derivative improved in properties at a low cost and providethe cellulose derivative improved in properties.

Solution to Problem

According to an aspect of the present invention, there is provided aprocess for producing a cellulose derivative, comprising:

a first step including

-   -   reacting a cellulose and a first reactant comprising a        long-chain reactant for reacting with a hydroxy group of the        cellulose to introduce a long-chain organic group having 5 or        more carbon atoms, in a solid-liquid heterogeneous system, to        form a cellulose derivative in a swollen state, the cellulose        derivative having the long-chain organic group having 5 or more        carbon atoms introduced therein and having a part of hydroxy        groups of the cellulose remained, and        -   performing solid-liquid separation to obtain the cellulose            derivative as an intermediate; and

a second step including reacting the intermediate cellulose derivativeand a second reactant comprising a short-chain reactant for reactingwith a remaining hydroxy group of the intermediate cellulose derivativeto introduce a short-chain organic group having 4 or less carbon atomsto form a final cellulose derivative having the short-chain organicgroup having 4 or less carbon atoms introduced therein.

According to another aspect of the present invention, there is provideda cellulose derivative produced by the aforementioned productionprocess.

According to another aspect of the present invention, there is provideda cellulose derivative comprising a long-chain organic group having 5 ormore carbon atoms and at least one short-chain organic group having 4 orless carbon atoms introduced therein by use of hydroxy groups of acellulose,

wherein the cellulose derivative has a crystal structure derived from acellulose derivative portion to which the short-chain organic grouphaving 4 or less carbon atoms is linked.

According to another aspect of the present invention, there is provideda molding resin composition containing the aforementioned cellulosederivative.

Advantageous Effects of Invention

According to an exemplary embodiment of the present invention, there isprovided a process for producing a cellulose derivative improved inproperties at a low cost, and provided the cellulose derivative improvedin properties.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a process chart illustrating a Production Example of acellulose derivative according to an exemplary embodiment of the presentinvention.

FIG. 2 is a process chart of a Production Example of a cellulosederivative according to related art.

FIG. 3 is a graph showing evaluation results of cellulose derivatives ofExamples and Reference Example by X-ray diffraction.

FIG. 4 is a graph showing evaluation results of cellulose derivatives ofExamples and Reference Example by X-ray diffraction.

DESCRIPTION OF EMBODIMENTS

In a production process according to an exemplary embodiment of thepresent invention, a cellulose derivative can be obtained in thefollowing two steps.

First, in the reaction of a first step, a cellulose and a long-chainreactant are reacted in a solid-liquid heterogeneous system andthereafter, solid-liquid separation is performed to obtain anintermediate cellulose derivative. The long-chain organic group can beintroduced into the cellulose by reacting hydroxy groups of thecellulose with the long-chain reactant. At this time, hydroxy groups ofthe cellulose are allowed to partly remain. According to this process,since the intermediate cellulose derivative produced after completion ofthe reaction is not dissolved in a solution, a large amount of solventfor use in reprecipitation is not required, with the result that energyrequired for a recovery step of a solvent, etc., can be reduced. Thesolid content (cellulose intermediate) obtained after the solid-liquidseparation can be, if necessary, washed and dried by a routine method.

In the following second step, hydroxy groups of the intermediatecellulose derivative and a short-chain reactant are reacted to obtain afinal cellulose derivative having a short-chain organic group introducedtherein. Since the number of hydrogen bonds between hydroxy groups ofthe cellulose reduces, the thermoplasticity and compatibility of thecellulose derivative with an additive are improved. Also in the secondstep, a product can be recovered without using a large amount of solventfor reprecipitation. For example, if a substance having a low boilingpoint, which can be separated by distillation from the final cellulosederivative, is used as a short-chain reactant or a solvent, separationbetween the reaction solution and a product (final cellulose derivative)can be performed by distillation without performing reprecipitation.

Now, the first step and second step will be further described below.

[First Step]

The reaction in a heterogeneous system of the first step for introducinga long-chain organic group is preferably performed in the state wherethe cellulose or a derivative thereof is impregnated with a firstreactant including a long-chain reactant to swell a cellulose or aderivative thereof. It is preferable that a cellulose or a derivativethereof is appropriately swollen in the beginning of the reaction step;however, a cellulose or a derivative thereof may not be swollen in thebeginning of the reaction step as long as a swollen state is obtaineduntil completion of the reaction step. If an appropriate swollen stateis obtained, a long-chain organic group having a larger number of carbonatoms can be easily introduced even in a solid-liquid heterogeneoussystem. At this time, the reaction is preferably performed in theconditions where a cellulose or a derivative thereof is hardly dissolvedin a liquid phase.

The degree of swelling of a cellulose derivative having a long-chainorganic group introduced therein preferably falls within the range of 10to 300% at least at the time of completion of a reaction step(immediately before solid-liquid separation). Note that the degree ofswelling can be determined in accordance with a measurement methoddescribed later. In view of reactivity, the degree of swelling ispreferably 20% or more, more preferably 30% or more and particularlypreferably 80% or more. In contrast, in view of the recovery rate of aproduct (solid content), the degree of swelling is preferably 200% orless, more preferably 150% or less and further preferably 100% or less.In order to obtain such a swollen state, it is preferable to use asolvent which provides a degree of swelling (determined by themeasurement method described later) of a long-chain organic groupintroduced cellulose derivative within the range of 10 to 300% inintroducing a long-chain organic group. In view of reactivity, it ispreferable to use a solvent providing a degree of swelling of preferably20% or more, more preferably 30% or more, particularly preferably 80% ormore. In contrast, in view of the recovery rate of a product (solidcontent), it is preferable to use a solvent providing a degree ofswelling of preferably 200% or less, more preferably 150% or less andfurther preferably 100% or less.

Similarly in view of the recovery rate of a product (solid content), thesolubility of a cellulose derivative (intermediate cellulose derivative)having a long-chain organic group introduced therein in a reactionsolution is preferably 10% by mass or less, further preferably 8% bymass or less and particularly preferably 5% by mass or less. As thesolubility, for example, the solubility of the cellulose derivativeproduced in chloroform can be used as a standard. In this case, thesolubility is preferably 10% by mass or less, further preferably 8% bymass or less and particularly preferably 5% by mass or less. Thesolubility herein refers to the mass ratio (percentage) of a solute (acellulose derivative having a long-chain organic group introducedtherein) dissolved in a saturated solution relative to the mass of thesaturated solution at 20° C.

In the intermediate cellulose derivative obtained in the reaction of thefirst step, part of hydroxy groups is allowed to remain. The remaininghydroxy groups serve as crosslinking sites between molecular chains ofintermediate cellulose derivatives by hydrogen bonding, with the resultthat dissolution of the intermediate cellulose derivative in a reactionsolution is suppressed and an appropriate swollen state can be realized.

The reaction in a heterogeneous system for introducing a long-chainorganic group may be performed in the presence of a solvent dissolving afirst reactant and an aprotic solvent is preferably used. Furthermore, areaction catalyst may be used, in particular, a basic catalyst ispreferable. Note that if a first reactant itself is a liquid, a reactionin a solid-liquid heterogeneous system can be performed without using asolvent.

The reaction in a heterogeneous system can be performed in the presenceof a short-chain reactant for introducing a short-chain organic group.The short-chain reactant is preferably a reactant which introduces anorganic group having 4 or less carbon atoms (short-chain organic group),and more preferably a short-chain acylating agent, which introduces ashort-chain acyl group having 2 to 4 carbon atoms. As the short-chainacylating agent, an acylating agent introducing an acetyl group or anacylating agent introducing a propionyl group is more preferable. Bothacylating agents may be used together and an acylating agent introducingan acetyl group is particularly preferable. The short-chain organicgroup can be introduced by substituting for the hydrogen atom of ahydroxy group of a cellulose.

As the long-chain reactant, a reactant introducing an organic grouphaving 5 or more carbon atoms (long-chain organic group) is preferable,and a long-chain acylating agent introducing a long-chain acyl grouphaving 5 to 48 carbon atoms is more preferable. As the long-chainacylating agent, a cardanol derivative can be used and the cardanolderivative preferably has an acid anhydride group. The acid anhydridegroup is favorable as a functional group to be reacted with a hydroxygroup of a cellulose. The long-chain organic group can be introduced bysubstituting for the hydrogen atom of a hydroxy group of a cellulose.

The starting cellulose to be used in the aforementioned productionprocesses may be subjected to an activation treatment. Owing to thistreatment, reactivity can be enhanced. As the activation treatment, anactivation treatment routinely performed to a cellulose can be applied.After completion of the activation treatment, the liquid (protonicsolvent such as acetic acid) used in the activation treatment may besubstituted with a liquid (for example, an aprotic solvent) which doesnot inhibit the reaction between a cellulose and a reactant. If asolvent is used in the reaction in a solid-liquid heterogeneous systembetween a cellulose and a reactant, substitution can be made with thesolvent.

[Second Step]

In the second step, the intermediate cellulose derivative obtained inthe first step, more specifically, the hydroxy groups remaining in theintermediate cellulose derivative, are reacted with a short-chainreactant (second reactant) to obtain a final cellulose derivative havingthe short-chain organic group introduced therein. The hydroxy groupsremaining in the intermediate cellulose derivative, since they formhydrogen bonds, sometimes inhibit thermoplasticity of the intermediatecellulose derivative and compatibility with an additive. In particular,a crystal region (cellulose crystal) in a cellulose, formed by hydrogenbonding of hydroxy groups, has low reactivity and likely to remain afterthe first step. The cellulose crystal, due to strong hydrogen bonding,has no thermoplasticity and poor compatibility with an additive. Incontrast, since the amount of remaining hydroxy groups decreases by thereaction of the second step, the final cellulose derivative is improvedin thermoplasticity and compatibility with an additive.

The short-chain reactant (second reactant) used in the second step ispreferably a reactant introducing an organic group having 4 or lesscarbon atoms (short-chain organic group), similarly to the short-chainreactant used in the first step, and more preferably a short-chainacylating agent introducing a short-chain acyl group having 2 to 4carbon atoms. A short-chain organic group can be introduced bysubstituting for at least a part of hydrogen atoms of the hydroxy groupsremaining in the cellulose derivative. As the short-chain acylatingagent, an acylating agent introducing an acetyl group or an acylatingagent introducing a propionyl group is more preferable. Both acylatingagents may be used together and an acylating agent introducing an acetylgroup is particularly preferable since a product and a reactant can beeasily separated. If a reactant having a relative low boiling point likean acylating agent introducing an acetyl group is used, a reactant canbe separated from a product, for example, by distillation and thus aproduct can be recovered without using a large amount of poor solvent.

As described above, according to the exemplary embodiment having a firststep of obtaining an intermediate cellulose derivative having along-chain organic group introduced therein by performing a reaction ina solid-liquid heterogeneous system followed by solid-liquid separationand a second step of introducing a short-chain organic group into theintermediate cellulose derivative, it is possible to obtain a cellulosederivative different in mechanical characteristic compared to thecellulose derivative obtained by performing a reaction in a solutionstate and performing reprecipitation. By use of a resin compositioncontaining such a cellulose derivative, a molded body improved inmechanical characteristics can be obtained.

The exemplary embodiment of the present invention will be furtherdescribed, below.

[Cellulose]

Cellulose is a straight-chain polymer obtained by polymerizingβ-D-glucose (β-D-glucopyranose) molecules represented by the followingformula (1) via β (1→4) glycoside bond. Each of glucose unitsconstituting cellulose has three hydroxy groups (where n represents anatural number). In the production process according to the exemplaryembodiment of the present invention, using these hydroxy groups, theshort-chain organic group and long-chain organic group can be introducedinto the cellulose.

Cellulose is a main component of plants and can be obtained by aseparation treatment for removing other components such as lignin fromplants. Other than those thus obtained, cotton (for example, cottonlinters) having a high cellulose content and pulp (for example, woodpulp) can be used directly or after they are purified. As the shape,size and form of the cellulose or a derivative thereof to be used as araw material, a powder form cellulose or a derivative thereof having anappropriate particle size and particle shape is preferably used in viewof reactivity, solid-liquid separation and handling. For example, afibrous or powdery cellulose or a derivative thereof having a diameterof 1 to 100 μm (preferably 10 to 50 μm) and a length of 10 μm to 100 mm(preferably 100 μm to 10 mm) can be used.

The polymerization degree of cellulose in terms of degree ofpolymerization of glucose (average polymerization degree) preferablyfalls within the range of 50 to 5000, more preferably 100 to 3000 andfurther preferably 500 to 3000. If the polymerization degree isextremely low, the strength and heat resistance of the produced resinmay not be sufficient in some cases. Conversely, if the polymerizationdegree is extremely high, the melt viscosity of the produced resin isextremely high, interfering with molding in some cases.

Cellulose may be mixed with chitin and chitosan having an analogousstructure. When cellulose is mixed with them, the amount thereof ispreferably 30% by mass or less relative to the total amount of mixture,preferably 20% by mass or less and further preferably 10% by mass orless.

The description in the above is directed to cellulose; however, thepresent invention is applicable to analogs of the cellulose, such asgeneral non-edible polysaccharides, i.e., chitin, chitosan,hemicellulose, glucomannan and curdlan.

[Long-Chain Organic Group]

In the first step of a process for producing a cellulose derivativeaccording to an exemplary embodiment of the present invention, along-chain organic group is introduced by use of a hydroxy group of acellulose.

The long-chain organic group can be introduced by reacting a hydroxygroup of a cellulose with a long-chain reactant. The long-chain organicgroup corresponds to an organic group moiety introduced in place of ahydrogen atom of a hydroxy group of a cellulose. Furthermore, at thelinking portion between a long-chain organic group and cellulose, forexample, an ester bond, an ether bond, a urethane bond, or carbonatebond is formed.

The long-chain reactant is a compound having at least one functionalgroup capable of reacting with a hydroxy group of a cellulose. If thelinking portion is an ester bond, a compound having a carboxyl group, acarboxylic acid halide group or a carboxylic acid anhydride group can beused as the long-chain reactant. If the linking portion is an etherbond, a compound having an epoxy group or a halogen group can be used asthe long-chain reactant. If the linking portion is a urethane bond, acompound having an isocyanate group can be used as the long-chainreactant. If the linking portion is a carbonate bond, a compound havinga chloroformate group can be used as the long-chain reactant.

The long-chain reactant may further contain an ester bond, an etherbond, a urethane bond, a carbonate bond and an amide bond in a molecularstructure other than the above functional group(s). Furthermore, thelong-chain reactant may contain at least one structure selected fromstructures of a chain hydrocarbon, an aromatic hydrocarbon and analicyclic hydrocarbon and may contain a structure of combination ofthese.

As the long-chain reactant, for example, a carboxylic acid having 5 to24 carbon atoms and a halide or acid anhydride of the carboxylic acidcan be used. The unsaturation degree and the position of an unsaturationbond of these carboxylic acids or carboxylic acid derivatives are notparticularly limited. Specific examples of the carboxylic acids, forexample, include pentanoic acid, caproic acid, enanthic acid, caprylicacid, pelargonic acid, capric acid, lauric acid, myristic acid,pentadecyl acid, palmitic acid, palmitoleic acid, margaric acid, stearicacid, oleic acid, vaccenic acid, linoleic acid, linolenic acid,eleostearic acid, tuberculostearic acid, arachidic acid, arachidonicacid, eicosenoic acid, behenic acid, erucic acid, lignoceric acid,hexadecadiene acid, hexadecatrienoic acid, octadecatetraenoic acid,octadecapentaenoic acid, icosatetraenoic acid, icosapentaenoic acid,docosapentaenoic acid and docosahexaenoic acid. Furthermore, as thecarboxylic acid, a carboxylic acid obtained from a natural product ispreferred in consideration of environment harmoniousness.

A long-chain organic group can be also formed by binding a compound lowin direct reactivity to a hydroxy group of cellulose, like a hydroxycompound, to cellulose by use of a multifunctional compound. Forexample, the multifunctional compound and a hydroxy compound can bebound by using a hydroxy group of the hydroxy compound and a functionalgroup of the multifunctional compound; and binding the obtained hydroxycompound derivative and a cellulose by using a hydroxy group of thecellulose and a functional group derived from the multifunctionalcompound. As the hydroxy compound, an alcohol and a phenol can bymentioned. As the phenol, for example, cardanol or a cardanol derivativeobtained by hydrogenating an unsaturated bond of the straight-chainhydrocarbon moiety is mentioned. Furthermore, the aromatic ring of thephenol moiety of a cardanol may be hydrogenated and converted into acyclohexane ring.

The above multifunctional compound preferably contains a hydrocarbongroup. The number of carbon atoms of the hydrocarbon group is preferably1 or more and more preferably 2 or more; and preferably 20 or less, morepreferably 14 or less and further preferably 8 or less. If the number ofcarbon atoms is extremely large, the size of the molecule is excessivelylarge, reducing the reactivity, with the result that it is sometimesdifficult to increase a reaction rate. As such a hydrocarbon group, adivalent group is preferable. Examples thereof include divalentstraight-chain aliphatic hydrocarbon groups (particularly, astraight-chain alkylene group) such as a methylene group, an ethylenegroup, a propylene group, a butylene group, a pentamethylene group, ahexamethylene group, a heptamethylene group, an octamethylene group, adecamethylene group, a dodecamethylene group and a hexadecamethylenegroup; divalent alicyclic hydrocarbon groups such as cycloheptane ring,a cyclohexane ring, a cyclooctane ring, a bicyclopentane ring, atricyclohexane ring, a bicyclooctane ring, a bicyclononane ring and atricyclodecane ring; divalent aromatic hydrocarbon groups such as abenzene ring, a naphthalene ring and a biphenylene group; and divalentgroups obtained by combining these.

As the functional group of a multifunctional compound as mentionedabove, a group selected from a carboxyl group, a carboxylic acidanhydride group, a carboxylic acid halide group (particularly,carboxylic acid chloride group), an epoxy group, an isocyanate group anda halogen group, is preferable. Of them, a carboxyl group, a carboxylicacid anhydride group, a halogen group (particularly, a chloride group)and an isocyanate group are preferable. If a cardanol or a hydrogenatedcardanol is used as the hydroxy compound, as the functional group to bereacted with a phenolic hydroxy group thereof, particularly, acarboxylic acid anhydride group, a halogen group (particularly, achloride group) and an isocyanate group are preferable. As thefunctional group to be reacted with a hydroxy group of cellulose,particularly a carboxylic acid anhydride group, a carboxylic acid halidegroup (particularly, a carboxylic acid chloride group) and an isocyanategroup are preferable. The carboxylic acid anhydride group can be formedby converting a carboxyl group into an acid anhydride. The carboxylicacid halide group can be formed by converting a carboxyl group into anacid halide.

As specific examples of such a multifunctional compound, dicarboxylicacid, carboxylic acid anhydride, dicarboxylic acid halide,monochlorocarboxylic acid and diisocyanates can be mentioned. Examplesof dicarboxylic acid include malonic acid, succinic acid, glutaric acid,pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, pentadecane dicarboxylic acid and hexadecanedicarboxylic acid. Examples of the carboxylic acid anhydride includeanhydrides of dicarboxylic acids of these. Examples of the dicarboxylichalide include acid halides of these dicarboxylic acids. Examples of themonochlorocarboxylic acid include monochloro acetate,3-chloropropionate, 3-fluoropropionic acid, 4-chlorobutyric acid,4-fluorobutyric acid, 5-chlorovaleric acid, 5-fluorovaleric acid,6-chlorohexanoic acid, 6-fluorohexanoic acid, 8-chlorooctanoic acid,8-fluorooctanoic acid, 12-chlorododecanoic acid, 12-fluorododecanoicacid, 18-chlorostearic acid and 18-fluorostearic acid. Examples of thediisocyanates include tolylene diisocyanate (TDI), 4,4′-diphenylmethanediisocyanate (MDI), 1,5-naphthylene diisocyanate (NDI), tolidinediisocyanate, 1,6-hexamethylene diisocyanate (HDI), isophoronediisocyanate (IPDI), xylylene diisocyanate (XDI), hydrogenated XDI,triisocyanate, tetramethyl xylene diisocyanate (TMXDI), 1,6,11-undecanetriisocyanate, 1,8-diisocyanatemethyl octane, lysine estertriisocyanate, 1,3,6-hexamethylene triisocyanate, bicycloheptanetriisocyanate and dicyclohexyl methane diisocyanate (HMDI; hydrogenatedMDI). Of them, as isocyanates, 4,4′-diphenylmethane diisocyanate (MDI)and 1,6-hexamethylene diisocyanate (HDI) can be preferably used.

As the long-chain organic group, a long-chain organic group having 5 ormore carbon atoms is included, and a long-chain organic group having 7or more carbon atoms is preferable, a long-chain organic group having 8or more carbon atoms is more preferable, a long-chain organic grouphaving 12 or more carbon atoms is further preferable and a long-chainorganic group having 16 or more carbon atoms is particularly preferablein order to obtain sufficient introduction effect of a long-chainorganic group. In view of reaction efficiency at the time a long-chainorganic group is introduced, a long-chain organic group having 48 orless carbon atoms is preferable, a long-chain organic group having 36 orless carbon atoms is more preferable and a long-chain organic grouphaving 25 or less carbon atoms is particularly preferable. An obtainedcellulose derivative may have a single type of long-chain organic group,or may have two or more types of long-chain organic group. If a desiredcellulose derivative has both a short-chain organic group and along-chain organic group, in order to sufficiently obtain the effectexpected from introduction of a short-chain organic group and the effectexpected from introduction of a long-chain organic group, the differencebetween the number of carbon atoms of a short-chain organic group andthe number of carbon atoms of a long-chain organic group is preferably 2or more, more preferably 3 or more and further preferably 5 or more.

The number of long-chain organic groups introduced per glucose unit ofcellulose (DS_(LO)) (an average value), in other words, the number ofhydroxy groups substituted per glucose unit of cellulose (the degree ofsubstitution of the hydroxy groups) (an average value) can beappropriately set depending upon the structure and introduction amountof short-chain organic group and the structure of long-chain organicgroup, physical properties required for a desired product, andsolid-liquid separation performance at the time of production. DS_(LO)can be set to fall within the range of, for example, 0.1 to 2.9 andpreferably 0.1 to 1.5. In order to obtain more sufficient introductioneffect of a long-chain organic group, DS_(LO) is preferably 0.2 or moreand more preferably 0.3 or more. In view of solid-liquid separationperformance at the time of production, DS_(LO) is preferably 2.8 orless, more preferably 1.5 or less and further preferably 1.0 or less.

The properties of a cellulose or a derivative thereof can be improved byintroducing a long-chain organic group as mentioned above into thecellulose or a derivative thereof. More specifically, water resistanceand thermoplasticity can be improved.

[Short-Chain Organic Group]

In the process for producing a cellulose derivative according to anexemplary embodiment of the present invention, a short-chain organicgroup can be introduced using a hydroxy group of a cellulose. In thefirst step, a short-chain organic group may be introduced simultaneouslywith a long-chain organic group. In this case, the types of short-chainorganic groups to be introduced in the first step and the second stepmay be the same or different. To simplify the process, short-chainorganic groups of the same type are preferably introduced.

The short-chain organic group can be introduced by reacting a hydroxygroup of a cellulose with a short-chain reactant. The short-chainorganic group corresponds to an organic group moiety introduced in placeof a hydrogen atom of a hydroxy group of a cellulose. The short-chainreactant is a compound having at least one functional group capable ofreacting with a hydroxy group of a cellulose. Examples thereof includehydrocarbon compounds having a carboxyl group, a carboxylic acid halidegroup, a carboxylic acid anhydride group, an isocyanate group, achloroformate group, an epoxy group, or a halogen group bound thereto.Specific examples thereof include an aliphatic monocarboxylic acid, andan acid halide or acid anhydride thereof; an aliphatic monoisocyanate;an aliphatic monochloroformate; aliphatic monoepoxide; and aliphaticmonohalide.

As the aliphatic monocarboxylic acid, a straight or branched (having aside chain) fatty acid is mentioned. Examples of the aliphaticmonoisocyanate include an aliphatic monoisocyanate having an isocyanategroup bound to a straight or branched (having a side chain) aliphatichydrocarbon. Examples of the aliphatic monochloroformate include analiphatic monochloroformate having a chloroformate group bound to astraight or branched (having a side chain) aliphatic hydrocarbon.Examples of the aliphatic monoepoxide include an aliphatic monoepoxidehaving an epoxy group bound to a straight or branched (having a sidechain) aliphatic hydrocarbon. Examples of the aliphatic monohalideinclude an aliphatic monohalides having a halogen group bound to astraight or branched (having a side chain) aliphatic hydrocarbon.

The short-chain organic group preferably has 2 to 4 carbon atoms andmore preferably 2 or 3 carbon atoms. A hydrogen atom of a hydroxy groupof a cellulose is preferably substituted with an acyl group having 2 to4 carbon atoms. The acyl group is preferably an acetyl group or apropionyl group. The acyl group may include both of these. The acylgroup is particularly preferably an acetyl group.

The number of short-chain organic groups introduced per glucose unit ofcellulose (DS_(SH)) (an average value), in other words, the number ofhydroxy groups substituted per glucose unit (the degree of substitutionof the hydroxy groups) (an average value) can be set to fall within therange of 0.1 to 2.5, preferably 0.2 to 2.3, and more preferably 0.5 to1.2, with respect to an intermediate cellulose derivative. Whereas, withrespect to a final cellulose derivative, DS_(SH) can be set to fallwithin the range of 0.1 to 2.9, preferably 0.5 to 2.9, more preferably1.3 to 2.7 and further preferably 1.3 to 2.5.

In the second step, the introduction amount (DS_(SH)) of short-chainorganic group to be introduced is preferably 0.1 or more, and morepreferably 0.2 or more. If a short-chain organic group is not introducedin the first step, the introduction amount (DS_(SH)) of short-chainorganic group to be introduced in the second step can be set to fallwithin the range of, for example 0.1 to 2.9, preferably 0.5 to 2.9, morepreferably 1.3 to 2.7 and further preferably 1.3 to 2.5. If ashort-chain organic group is introduced in the first step, theintroduction amount (DS_(SH)) of short-chain organic group to beintroduced in the second step can be set to fall within the range of,for example, 0.1 to 2.7, preferably 0.2 to 2.5 and more preferably 0.3to 2.0.

By introducing the aforementioned short-chain organic group into acellulose or a derivative thereof, the intermolecular force(intermolecular bond) of the cellulose can be reduced. In particular,since the number of hydroxy groups remaining after the first step isreduced by the reaction of the second step, thermoplasticity of thecellulose derivative and affinity thereof for an additive are improved.

[Crosslinking Site in Cellulose Derivative]

In a production process according to an exemplary embodiment of thepresent invention, a starting cellulose and a cellulose derivative aftercompletion of the reaction preferably have a crosslinking site so as tosuppress dissolution in a liquid phase (or solvent) and obtain anappropriate swollen state.

The crosslinking site refers to an intramolecular bond of cellulose (ora derivative thereof) including a chemical bond and a physical bond.Examples of the bond include a hydrogen bond between hydroxy groups ofcellulose and a hydrogen bond between a hydroxy group of cellulose (or aderivative thereof) and an organic group introduced. As the crosslinkingsite, a crosslinking site derived from a crystal of cellulose can beused. Furthermore, the crosslinking site includes a bond due to tanglingbetween main chains of cellulose (or derivatives thereof) and may betangling between mutual organic groups introduced and tangling between amain chain of a cellulose (or a derivative thereof) and an organic groupintroduced. The crosslinking site may be an aggregation site of a partof a cellulose derivative, the site of which is formed as a result thataffinity to a liquid phase (or solvent) is changed by introduction of anorganic group, i.e., affinity to a liquid phase (or solvent) is locallyreduced. The crosslinking site may be bond of a crosslinking agentcapable of binding to a reactive functional group of cellulose and maybe a bond of a crosslinking agent capable of physically binding to acellulose molecular chain. The crosslinking agent may be an impurityderived from a plant raw material such as hemicellulose and lignin. Thecrosslinking site may be constituted of a combination of two or morebinding sites.

It is sometimes difficult to directly measure the amount of crosslinkingsites present depending on the binding structure as mentioned above;however, the amount can be indirectly measured and can be set to fallwithin a desired range. The amount of crosslinking site present can beindirectly determined by determining a degree of swelling of a cellulosederivative in a solvent having affinity to the cellulose derivative, forexample, can be determined by a method for determining a degree ofswelling (described later).

[Remaining Amount of Hydroxy Group in a Cellulose Derivative]

In view of the production process in the first step, as the amount ofhydroxy group increases, the solid-liquid separation performance of thecellulose derivative tends to increase. Furthermore, in view of physicalproperties, as the amount of hydroxy group increases, maximum strengthand heat resistance of the cellulose derivative tend to increase;whereas water absorbability tends to increase. In contrast, as theconversion rate (degree of substitution) of hydroxy groups increases,water absorbability tends to decrease, plasticity and breaking straintend to increase; whereas, maximum strength and heat resistance tend todecrease. In consideration of these tendencies and, reaction conditionsof the short-chain reactant and the long-chain reactant, the conversionrate of hydroxy groups can be appropriately set.

The number of remaining hydroxy groups per glucose unit of anintermediate cellulose derivative obtained in the first step (hydroxygroup remaining degree) (average value) can be set within the range of0.1 to 2.8. In view of the solid-liquid separation performance in thefirst step and introduction of a short-chain organic group in thesubsequent second step, the hydroxy group remaining degree is preferably0.2 or more, further preferably 0.8 or more and particularly preferably1.5 or more.

The number of remaining hydroxy groups per glucose unit of a finalcellulose derivative (hydroxy group remaining degree) (average value)can be set to fall within the range of 0 to 2.8. In view of e.g.,maximum strength and heat resistance, hydroxy groups may remain; forexample, the hydroxy group remaining degree may be 0.01 or more andfurther 0.1 or more. Particularly in view of flowability, the hydroxygroup remaining degree of a final cellulose derivative is preferably 0.1or more and less than 1.7, more preferably 1.2 or less and particularlypreferably 0.5 or less. If the hydroxy group remaining degree is below0.1, the ratio of a short-chain linked cellulose derivative portionrelatively low in flowability tends to increase, with the result thatthe flowability improving effect cannot be sufficiently obtained. Incontrast, if the hydroxy group remaining degree is beyond 1.7, the ratioof unreacted cellulose low in flowability increases, with the resultthat the flowability of the entire cellulose derivative tends todecrease.

[Production Process]

Now, a production process according to an exemplary embodiment of thepresent invention will be further described below.

[First Step] [Activation of Cellulose]

Before the reaction step for introducing a long-chain organic group intocellulose, an activation treatment (pretreatment step) can be performedin order to increase the reactivity of the cellulose. As the activationtreatment, an activation treatment which is routinely performed beforeacetylation of cellulose can be applied.

In the activation treatment employed in the production process accordingto an exemplary embodiment of the present invention, a cellulose isswollen by bringing the cellulose into contact with a solvent, forexample, by a method of spraying an activation solvent having affinityfor a cellulose to the cellulose or by a method (soaking method) ofsoaking a cellulose in an activation solvent. Owing to the treatment, areactant easily penetrates between cellulose molecular chains (if asolvent and a catalyst are used, a reactant easily penetrates togetherwith these), with the result that the reactivity of the celluloseimproves. Herein, examples of the activation solvent include water;carboxylic acids such as acetic acid, propionic acid, butyric acid,valeric acid, caproic acid, enanthic acid, caprylic acid and pelargonicacid; alcohols such as methanol, ethanol, propanol and isopropanol;nitrogen-containing compounds such as dimethylformamide, formamide andethanolamine; and sulfoxide compounds such as dimethylsulfoxide. Thesecan be used in combination of two or more types. Particularlypreferably, water, acetic acid and dimethylsulfoxide can be used.

The use amount of activation solvent relative to a cellulose (100 partsby mass) can be set to be, for example, 10 parts by mass or more,preferably 20 parts by mass or more and more preferably 30 parts by massor more. If a cellulose is soaked in an activation solvent, the useamount of activation solvent relative to the cellulose in term of mass,can be set to be, for example, the same or more, preferably 5 times ormore and more preferably 10 times or more. In view of load for removingthe activation solvent after the pretreatment and cost reduction ofmaterials, the use amount of activation solvent is preferably 300 timesor less, more preferably 100 times or less and further preferably 50times or less.

The temperature of the activation treatment can be appropriately setwithin the range of, for example, 0 to 100° C. In view of the efficiencyof activation and reduction of energy cost, the temperature ispreferably 10 to 40° C. and more preferably 15 to 35° C.

The time for the activation treatment can be appropriately set withinthe range of, for example, 0.1 hour to 72 hours. In order to performsufficient activation and reduce the treatment time, the time ispreferably 0.1 hour to 24 hours and more preferably 0.5 hours to 3hours.

After the activation treatment, an excessive activation solvent can beremoved by a solid-liquid separation method such as suction filtration.

If a solvent is used in a reaction for introducing an organic group, theactivation solvent contained in a cellulose can be substituted with thesolvent to be used in the reaction after the activation treatment. Forexample, a substitution treatment can be performed in accordance withthe soaking method for an activation treatment mentioned above bychanging the activation solvent to the solvent to be used in thereaction.

[Reaction of the First Step] Introduction of Long-Chain Organic Group(or Long-Chain Organic Group and Short-Chain Organic Group)

To a cellulose or a cellulose to which the above activation treatmentwas applied, a long-chain organic group (or a long-chain organic groupand a short-chain organic group) is introduced. Note that, a method ofintroducing a short-chain organic group and a long-chain organic groupby use of a short-chain reactant and a long-chain reactant will bedescribed; however, a cellulose derivative having a long-chain organicgroup alone introduced therein can be produced in the same manner asabove except that a short-chain reactant is not used.

In the reaction step, a short-chain reactant and a long-chain reactantas mentioned above, if necessary, a solvent and a catalyst are mixedwith a cellulose. The cellulose, the short-chain reactant and thelong-chain reactant can be reacted in a solid-liquid heterogeneoussystem. At this time, if necessary, heating or stirring can beperformed. The types of the reactive functional groups of theshort-chain reactant and long-chain reactant are preferably the same.Note that, if the above reactants are acid anhydrides, a mixed acidanhydride of a long-chain organic acid and a short-chain organic acid(asymmetric acid anhydride) can be used. The mixed acid anhydride servesas a long-chain reactant as well as a short-chain reactant.

In the reaction step, a cellulose is soaked in a reaction solutioncontaining the short-chain reactant and the long-chain reactant to swellthe cellulose. The cellulose in this state can be reacted. Owing tothis, the short-chain reactant and the long-chain reactant can easilypenetrate between cellulose molecular chains, with the result that thereactivity improves.

The use amount of reaction solvent relative to the cellulose in terms ofmass can be set to be, for example, the same or more, preferably fivetimes or more, and more preferably 10 times or more. In view of e.g.,load for removing a reaction solution after completion of a reaction andcost reduction of materials, the use amount of the reaction solvent ispreferably 300 times or less, more preferably 100 times or less, furtherpreferably 50 times or less and particularly preferably 30 times orless.

The reaction temperature is preferably 10° C. or more, more preferably20° C. or more and further preferably 30° C. or more in view of reactionefficiency etc. In view of e.g., suppression of decomposition reactionand reduction in energy cost, the reaction temperature is preferably200° C. or less, more preferably 150° C. or less and further preferably100° C. or less.

The reaction time is preferably 0.5 hours or more and more preferablyone hour or more in order to sufficiently conduct a reaction, andpreferably 24 hours or less and more preferably 12 hours or less in viewof e.g., efficiency of the production process.

If a solvent is used, a solvent having high affinity for a long-chainand short-chain linked cellulose derivative (or long-chain linkedcellulose derivative) i.e., an intermediate product, is preferably used.A solvent capable of dissolving a general short-chain linked cellulosederivative having no crosslinking site or a solvent capable ofdissolving a general long-chain and short-chain linked cellulosederivative having no crosslinking site can be used. As such a solvent,which can be appropriately selected depending upon the amount ofremaining hydroxy groups in a cellulose derivative and thehydrophobicity and introduction amount of the short-chain organic groupand long-chain organic group, an aprotic solvent is preferable, andparticularly, a proton-affinity solvent capable of forming a hydrogenbond with a hydroxy group of cellulose is preferable.

Examples of such a high affinity solvent include a hetero cycliccompound, an ether, an amide, a ketone, an ester, a polar halogenatedhydrocarbon, a carbonate, a nitro compound, a nitrile and anorganosulfur compound. Examples of the hetero cyclic compound includecyclic ethers (dioxane, tetrahydrofuran, dioxolane, etc.) andheteroarene (pyridine, quinoline, etc.). Examples of ether having highaffinity include, other than the above cyclic ethers, non-cyclic ethershaving a plurality of ether structures such as 1,2-dimethoxyethane anddiethylene glycol dimethyl ether and ethers having an aryl group such asmethylphenyl ether and diphenyl ether. Examples of the amides includeN-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.Examples of the ketone include acetone, methyl ethyl ketone, methylisobutyl ketone and cyclohexanone. Examples of the ester include methylformate, methyl acetate, ethyl acetate, butyl acetate and methylcellosolve acetate. Examples of the polar halogenated hydrocarboninclude chloroform, methylene chloride, dichloroethane, propylenechloride and tetrachloroethane. Examples of the carbonate includepropylene carbonate and butylene carbonate. Examples of the nitrocompound include nitromethane and nitropropane. Examples of the nitrileinclude acetonitrile and benzonitrile. Examples of the organosulfurcompound include sulfoxide compounds such as dimethylsulfoxide. Thesesolvents may be used as a mixture of two or more. Owing to use of such asolvent as mentioned above, a satisfactory swollen state of a cellulosederivative is formed and the effect of steric hindrance is reduced andthe reactivity of a reactant can be increased.

In the course of a reaction, the same or different type of solvent maybe appropriately added.

Note that, the “general long-chain and short-chain linked cellulosederivative (or short-chain linked cellulose derivative) having nocrosslinking site” corresponds to a long-chain and short-chain linkedcellulose derivative (or short-chain linked cellulose derivative)obtained by performing a reaction using a solvent capable of dissolvinga product, adding a poor solvent to the reaction solution dissolving theproduct to precipitate the product and performing solid-liquidseparation.

If a catalyst is used, the catalyst can be appropriately selecteddepending upon the type of short-chain reactant or long-chain reactantand then put in use. If the reactant is, for example, a carboxylic acidand a carboxylic acid anhydride, an acid catalyst, a base catalyst and ametal-based catalyst can be used. Examples of the acid catalyst includeinorganic acids (sulfuric acid, perchloric acid, hydrochloric acid,etc.) and organic acids (methane sulfonic acid, toluene sulfonic acid,etc.). Examples of the base catalyst include pyridine derivatives(dimethylaminopyridine (DMAP), 4-pyrrolidinopyridine, etc.), imidazoles(1-methylimidazole, 1,2-dimethylimidazole, etc.) and amidines(diazabicyclo undecene (DBU), diazabicyclononene, etc.). In view ofreactivity, DMAP and DBU are preferable, and particularly DMAP ispreferable. Examples of the metal-based catalyst include metal chlorides(iron chloride, aluminum chloride, indium chloride, basic zirconiumchloride, zinc chloride, cobalt chloride, nickel chloride, copperchloride, etc.), metal nitrates (compounds obtained by substitutingchloride ions of the aforementioned metal chlorides with nitric acidions, etc.), metal sulfates (compounds obtained by substituting chlorideions of the aforementioned metal chlorides with sulfuric acid ions,etc.) and metal acetic acid salts (compounds obtained by substitutingchloride ions of the aforementioned metal chlorides with acetic acidions, etc.).

If a proton-affinity solvent is used as a solvent, a base catalyst ispreferable.

If the reactant is an isocyanate, an organic metal catalyst and a basecatalyst can be used. Examples of the organic metal catalyst include tinoctylate and dibutyltin dilaurate. Examples of the base catalyst includetriethylene diamine and trimethyl aminoethyl piperazine.

[Recovery of Product (Solid-Liquid Separation)]

The product in the first step, i.e., a long-chain and short-chain linkedcellulose derivative (or long-chain linked cellulose derivative), sinceit at least has crosslinking sites consisting of remaining hydroxygroups, tends to have low solubility to a reaction solution. Thus, theproduct can be easily recovered by a general solid-liquid separationtreatment. Examples of the solid-liquid separation treatment includefiltration (natural filtration, filtration under reduced pressure,pressure filtration, centrifugal filtration and hot filtration ofthese), spontaneous precipitation/levitation, liquid separation,centrifugation and compression. These may be used in an appropriatecombination. In a production process of the first step according to theexemplary embodiment, a step of precipitating and recovering a productdissolved in a reaction solution with a large amount of poor solvent canbe omitted. Thus, the production process has low energy load in therecovery step, compared to a production process of the related artrequiring such precipitation and recovery.

The solid content obtained by the solid-liquid separation may be, ifnecessary, washed and dried by a general method.

[Second Step] [Reaction of Second Step] Introduction of Short-ChainOrganic Group

In the second step, the intermediate cellulose derivative obtained inthe first step, more specifically, hydroxy groups remaining in theintermediate cellulose derivative, are reacted with a short-chainreactant (second reactant) to obtain a final cellulose derivative.

In the reaction step, a short-chain reactant as mentioned above, and, ifnecessary, a solvent and a catalyst are mixed with the intermediatecellulose derivative, and the short-chain reactant can be reacted withthe intermediate cellulose derivative. At this time, if necessary,heating and stirring can be made.

The use amount of reaction solvent relative to the intermediatecellulose derivative in terms of mass can be set to be, for example, thesame or more, preferably twice or more. In view of e.g., load forremoving the reaction solution after completion of the reaction and costreduction of materials, the use amount is more preferably 100 times orless and further preferably 50 times or less and particularly preferably20 times or less. Note that, in the second step, since a short-chainreactant having a relatively low degree of steric hindrance is reacted,the degree of swelling of a cellulose derivative in a reaction solutionand the solubility thereof can be reduced compared to those in the firststep in which a long-chain reactant having a high degree of sterichindrance is reacted. Thus, in the second step, the use amount ofreaction solution can be reduced compared to that of the first step.

The reaction temperature is preferably 10° C. or more, more preferably20° C. or more and further preferably 30° C. or more in view of reactionefficiency etc. In view of e.g., suppression of decomposition reactionand reduction in energy cost, the reaction temperature is preferably200° C. or less, more preferably 150° C. or less and further preferably100° C. or less.

The reaction time is preferably 0.5 hours or more and more preferablyone hour or more in order to sufficiently conduct a reaction, andpreferably 24 hours or less in view of e.g., efficiency of theproduction process.

If a solvent is used, a solvent having high affinity for a finalproduct, i.e., a long-chain and short-chain linked cellulose derivative,is preferably used, and a solvent capable of dissolving a generalshort-chain linked cellulose derivative having no crosslinking site or asolvent capable of dissolving a general long-chain and short-chainlinked cellulose derivative having no crosslinking site can be used. Asa solvent, which can be appropriately selected depending upon the amountof remaining hydroxy groups in a cellulose derivative and thehydrophobicity and introduction amount of short-chain organic group andlong-chain organic group, an aprotic solvent is preferable, andparticularly, a proton-affinity solvent capable of forming a hydrogenbond with a hydroxy group of cellulose is preferable. As describedlater, in view of a recovery process for recovering the product of thesecond step by distillation, a solvent having a low boiling point ispreferably used.

Examples of such a high affinity solvent include a hetero cycliccompound, an ether, an amide, a ketone, an ester, a polar halogenatedhydrocarbon, a carbonate, a nitro compound, a nitrile and anorganosulfur compound. Examples of the hetero cyclic compound includecyclic ethers (dioxane, tetrahydrofuran, dioxolane, etc.) andheteroarene (pyridine, quinoline, etc.). Examples of ether having highaffinity include, other than the above cyclic ethers, non-cyclic ethershaving a plurality of ether structures such as 1,2-dimethoxyethane anddiethylene glycol dimethyl ether and ethers having an aryl group such asmethylphenyl ether and diphenyl ether. Examples of the amides includeN-methylpyrrolidone, N,N-dimethylformamide and N,N-dimethylacetamide.Examples of the ketone include acetone, methyl ethyl ketone, methylisobutyl ketone and cyclohexanone. Examples of the ester include methylformate, methyl acetate, ethyl acetate, butyl acetate and methylcellosolve acetate. Examples of the polar halogenated hydrocarboninclude chloroform, methylene chloride, dichloroethane, propylenechloride and tetrachloroethane. Examples of the carbonate includepropylene carbonate and butylene carbonate. Examples of the nitrocompound include nitromethane and nitropropane. Examples of the nitrileinclude acetonitrile and benzonitrile. Examples of the organosulfurcompound include sulfoxide compounds such as dimethylsulfoxide. Thesesolvents may be used as a mixture two or more. Owing to use of such asolvent as mentioned above, a satisfactory swollen state or dissolvedstate of a cellulose derivative is formed and the effect of sterichindrance is reduced and the reactivity of a reactant can be increased.

In the middle of a reaction, the same or different type of solvent maybe appropriately added.

Note that, the “general long-chain and short-chain linked cellulosederivative having no crosslinking site (or short-chain linked cellulosederivative)” corresponds to a long-chain and short-chain linkedcellulose derivative (or short-chain linked cellulose derivative)obtained by performing a reaction using a solvent capable of dissolvinga product, adding a poor solvent to the reaction solution dissolving theproduct to precipitate the product, and performing solid-liquidseparation.

If a catalyst is used, the catalyst can be appropriately selecteddepending upon the type of short-chain reactant and then put in use. Ifthe reactant is, for example, a carboxylic acid and a carboxylic acidanhydride, an acid catalyst, a base catalyst and a metal-based catalystcan be used. Examples of the acid catalyst include inorganic acids(sulfuric acid, perchloric acid, hydrochloric acid, etc.) and organicacids (methane sulfonic acid, toluene sulfonic acid, etc.). Examples ofthe base catalyst include pyridine derivatives (dimethylaminopyridine(DMAP), 4-pyrrolidinopyridine, etc.), imidazoles (1-methylimidazole,1,2-dimethylimidazole, etc.) and amidines (diazabicyclo undecene (DBU),diazabicyclononene, etc.). In view of reactivity, DMAP and DBU arepreferable, and particularly DMAP is preferable. Examples of themetal-based catalyst include metal chlorides (iron chloride, aluminumchloride, indium chloride, basic zirconium chloride, zinc chloride,cobalt chloride, nickel chloride, copper chloride, etc.), metal nitrates(compounds obtained by substituting chloride ions of the aforementionedmetal chlorides with nitric acid ions, etc.), metal sulfates (compoundsobtained by substituting chloride ions of the aforementioned metalchlorides with sulfuric acid ions, etc.) and metal acetic acid salts(compounds obtained by substituting chloride ions of the aforementionedmetal chlorides with acetic acid ions, etc.).

If a proton-affinity solvent is used, a base catalyst is preferable.

If the reactant is isocyanate, an organic metal catalyst and a basecatalyst can be used. Examples of the organic metal catalyst include tinoctylate and dibutyltin dilaurate. Examples of the base catalyst includetriethylenediamine and trimethyl aminoethyl piperazine.

[Recovery of Product]

The final cellulose derivative to be obtained in the second step can berecovered from the reaction solution in accordance with a generalrecovery method, which is not particularly limited. If a cellulosederivative is not dissolved in the reaction solution, a method in whicha solid-liquid separation is conducted to separate the product from thereaction solution is preferable in view of production energy; whereas ifa cellulose derivative is dissolved or mixed in the reaction solutionand thus it is difficult to perform solid-liquid separation, a method inwhich the reaction solution is distilled to recover the remainingcellulose derivative is preferable.

In the distillation of the reaction solution, a short-chain reactant anda reaction solvent preferably have a low boiling point. In particular,as the reactant, a reactant which introduces an acetyl group ispreferable. Furthermore, when a reaction solution is distilled, acatalyst is preferably not used. When a catalyst is used, a catalysthaving a low boiling point is preferable; however, a catalyst may not beremoved by distillation but removed from a product with e.g., a cleaningsolvent. Moreover, when a reaction solution is distilled, distillationmay be terminated at the time when a cellulose derivative precipitates,and then the remaining reaction solution and the cellulose derivativecan be separated by solid-liquid separation to recover the cellulosederivative.

[Dissociation of Crosslinking Site]

After an organic group is introduced, the crosslinking site of acellulose derivative, if necessary, can be dissociated. Reducing thenumber of hydrogen bonds by substitution of hydroxy groups in the secondstep is one of dissociation methods. Additional dissociation can beseparately performed. If additional dissociation is performed, further,thermoplasticity of a cellulose derivative and compatibility thereofwith an additive can be improved.

As a method of dissociating crosslinking sites including the method tobe used in the second step, heating, addition of a plasticizer, additionof a solvent, addition of a reactive organic substance or an inorganicsubstance for reacting with the linking sites and dissociating thesites, irradiation with an electromagnetic wave such as a UV ray, anelectron beam and a neutron beam, are mentioned. Heating or addition ofa plasticizer may be performed at the time of melting and kneading aproduct. As the plasticizer, various types of additives described latercan be used. If crosslinking is due to a hydrogen bond formed withhydroxy groups in a cellulose derivative, a method of dissociating ahydrogen bond is effective; for example, a substance capable ofdissociating a hydrogen bond can be added. As the substance capable ofdissociating a hydrogen bond, for example, a substance reacting with ahydroxy group to eliminate the hydroxy group (for example, substitutingthe hydrogen atom of a hydroxy group or converting the hydroxy group toanother functional group) is mentioned. Alternatively, a plasticizer andan ion liquid are mentioned. As the substance to be reacted with ahydroxy group, a short-chain reactant and long-chain reactant asmentioned above can be used.

[Physical Properties of Product (Organic Group-Introduced CelluloseDerivative)]

The cellulose derivative obtained by a production process according toan exemplary embodiment of the present invention is reduced inintermolecular force (crosslinking sites) compared to a cellulose sincean organic group (a short-chain organic group and long-chain organicgroup) is introduced by use of a hydroxy group of a cellulose. Inaddition, since the long-chain organic group introduced serves as aninternal plasticizer, such an organic group-introduced cellulosederivative can exhibit satisfactory thermoplasticity. If a long-chainorganic group having high hydrophobicity is used, water resistance canbe further enhanced.

Such an organic group introduced cellulose derivative can possess acrystal structure derived from a short-chain linked cellulose derivativeportion. The intermediate cellulose derivative obtained in the firststep has remaining hydroxy groups, which tend to remain in alow-reactive cellulose crystal. However, if the remaining hydroxy groupsare substituted with short-chain organic groups in the second step, theamount of cellulose crystal reduces and a crystal of a short-chainlinked cellulose derivative portion can be newly produced. As theshort-chain linked cellulose derivative portion, for example, portionsof a cellulose acetate structure, a cellulose propionate structure and acellulose butyrate structure can be mentioned. In particular, if theamount of short-chain organic group linked increases, all hydroxy groupsin a glucose unit are substituted with short-chain organic groups, withthe result that a cellulose triacetate structure, a cellulosetripropionate structure and a cellulose tributyrate structure tend to beproduced. If the crystal of the short-chain linked cellulose derivativeportion has polymorphisms, all of the polymorphisms are possiblypresent. For example, in the case of a cellulose triacetate (CTA)portion, both of polymorphisms called as CTA-I and CTA-II are possiblypresent.

The crystal of a short-chain linked cellulose derivative portion can beevaluated, for example, by X-ray diffraction. At the time of evaluation,if a cellulose derivative is, for example, pressed to increase thedensity, confirmation of signals can be made easier.

[Molding Resin Composition and Additive]

The organic group-introduced cellulose derivative according to anexemplary embodiment of the present invention can provide a resincomposition suitable as a molding material by adding additives inaccordance with desired properties. In particular, since the remaininghydroxy groups are substituted with short-chain organic groups in thesecond step, the final cellulose derivative obtained in the exemplaryembodiment has a high compatibility with an additive compared to theintermediate cellulose derivative obtained in the first step. The finalcellulose derivative can be compatible with an additive which iscompatible with a general cellulose derivative.

To the cellulose derivative according to an exemplary embodiment of thepresent invention, various types of additives usually used inthermoplastic resins can be applied. For example, if a plasticizer isadded, thermoplasticity and breaking elongation can be more improved.Examples of such a plasticizer include phthalic esters such as dibutylphthalate, diaryl phthalate, diethyl phthalate, dimethyl phthalate,di-2-methoxyethyl phthalate, ethyl phthalyl ethyl glycolate and methylphthalyl ethyl glycolate; tartaric acid esters such as dibutyl tartrate;adipic acid esters such as dioctyl adipate and diisononyl adipate;polyhydric alcohol esters such as triacetin, diacetyl glycerin,tripropionitrile glycerin and glyceryl monostearate; phosphoric acidesters such as triethyl phosphate, triphenyl phosphate and tricresylphosphate; dibasic fatty acid esters such as dibutyl adipate, dioctyladipate, dibutyl azelate, dioctyl azelate and dioctyl sebacate; citricacid esters such as triethyl citrate, acetyltriethyl citrate andtributyl acetylcitrate; epoxylated vegetable oils such as epoxylatedsoybean oil and epoxylated linseed oil; castor oil and a derivativethereof; benzoic acid esters such as ethyl O-benzoyl benzoate; aliphaticdicarboxylic acid esters such as sebacate and azelate; unsaturateddicarboxylic acid esters such as maleate; and N-ethyl toluenesulfonamide, triacetin, O-cresyl p-toluenesulfonate and tripropionin.Particularly of them, if a plasticizer such as dioctyl adipate, benzyladipate-2 butoxyethoxyethyl, tricresyl phosphate, diphenylcresylphosphate or diphenyl octyl phosphate is added, not onlythermoplasticity and breaking elongation but also shock resistance canbe effectively improved.

Examples of other plasticizers include cyclohexane dicarboxylic acidesters such as dihexyl cyclohexanedicarboxylate, dioctylcyclohexanedicarboxylate and di-2-methyloctyl cyclohexanedicarboxylate;trimellitic acid esters such as dihexyl trimellitate, diethylhexyltrimellitate and dioctyl trimellitate; and pyromellitic acid esters suchas dihexyl pyromellitate, diethylhexyl pyromellitate and dioctylpyromellitate.

To the cellulose derivative according to an exemplary embodiment of thepresent invention, if necessary, an inorganic or organic granular orfibrous filler can be added. By adding a filler, strength and rigiditycan be more improved. Examples of the filler include, mineral particles(talc, mica, baked siliceous earth, kaolin, sericite, bentonite,smectite, clay, silica, quartz powder, glass beads, glass powder, glassflake, milled fiber, Wollastonite, etc.), boron-containing compounds(boron nitride, boron carbonate, titanium boride etc.), metal carbonates(magnesium carbonate, heavy calcium carbonate, light calcium carbonate,etc.), metal silicates (calcium silicate, aluminum silicate, magnesiumsilicate, magnesium aluminosilicate, etc.), metal oxides (magnesiumoxide etc.), metal hydroxides (aluminum hydroxide, calcium hydroxide,magnesium hydroxide, etc.), metal sulfates (calcium sulfate, bariumsulfate, etc.), metal carbides (silicon carbide, aluminum carbide,titanium carbide, etc.), metal nitrides (aluminum nitride, siliconnitride, titanium nitride, etc.), white carbon and metal foils. Examplesof the fibrous filler include organic fibers (natural fiber, papersetc.), inorganic fibers (glass fiber, asbestos fiber, carbon fiber,silica fiber, silica alumina fiber, Wollastonite, zirconia fiber,potassium titanate fiber etc.) and metal fibers. These fillers can beused singly or in combination of two or more types.

To the cellulose derivative according to an exemplary embodiment of thepresent invention, if necessary, a flame retardant can be added. Byadding a flame retardant, flame resistance can be imparted. Examples ofthe flame retardant include metal hydrates such as magnesium hydroxide,aluminum hydroxide and hydrotalcite, basic magnesium carbonate, calciumcarbonate, silica, alumina, talc, clay, zeolite, bromine-based flameretardant, antimony trioxide, phosphoric acid based flame retardant(aromatic phosphate, aromatic condensed phosphate, etc.), compoundscontaining phosphorus and nitrogen (phosphazene compound), etc. Theseflame retardants can be used singly or in combination with two or moretypes.

To the cellulose derivative according to an exemplary embodiment of thepresent invention, if necessary, a shock resistance improver can beadded. By adding a shock resistance improver, shock resistance can beimproved. Examples of the shock resistance improver include a rubbercomponent and a silicone compound. Examples of the rubber componentinclude a natural rubber, epoxylated natural rubber and synthesizedrubber. Furthermore, examples of the silicone compound include organicpolysiloxane formed by polymerization of alkyl siloxane, alkyl phenylsiloxane, etc. and modified silicone compounds obtained by modifying aside chain or an end of an organic polysiloxane as mentioned above withpolyether, methylstyryl, alkyl, higher fatty acid ester, alkoxy,fluorine, an amino group, an epoxy group, a carboxyl group, a carbinolgroup, a methacryl group, a mercapto group, a phenol group etc. Theseshock resistance improvers can be used singly or in combination of twoor more types.

As the silicone compound, a modified silicone compound (modifiedpolysiloxane compound) is preferred. As the modified silicone compound,a modified polydimethyl siloxane is preferred, which has a structurehaving a main chain constituted of dimethyl siloxane repeat units and aside chain or a terminal methyl group partly substituted with an organicsubstituent containing at least one group selected from an amino group,an epoxy group, a carbinol group, a phenol group, a mercapto group, acarboxyl group, a methacryl group, a long-chain alkyl group, an aralkylgroup, a phenyl group, a phenoxy group, an alkyl phenoxy group, along-chain fatty acid ester group, a long-chain fatty acid amide groupand a polyether group. The modified silicone compound, because of thepresence of such an organic substituent, is improved in affinity for theaforementioned cellulose derivative and dispersibility in the cellulosederivative is improved. Consequently, a resin composition excellent inshock resistance can be obtained.

As such a modified silicone compound, a modified silicone compoundproduced in accordance with a conventional method can be used.

Examples of the organic substituent contained in the modified siliconecompound include the organic substituents represented by the followingformulas (2) to (20) are mentioned:

where a and b each represent an integer of 1 to 50.

In the aforementioned formulas, R¹ to R¹⁰, R¹² to R¹⁵, R¹⁹ and R²¹ eachrepresent a divalent organic group. Examples of the divalent organicgroup include alkylene groups such as a methylene group, an ethylenegroup, a propylene group and a butylene group; alkyl arylene groups suchas a phenylene group and a tolylene group; oxyalkylene groups andpolyoxyalkylene groups such as —(CH₂—CH₂—O)c- (c represents an integerfrom 1 to 50), —[CH₂—CH (CH₃)—O]_(d)— (d represents an integer from 1 to50), and —(CH₂)e-NHCO— (e represents an integer from 1 to 8). Of these,an alkylene group is preferable and particularly, an ethylene group anda propylene group are preferable.

In the aforementioned formulas, R¹¹, R¹⁶ to R¹⁸, R²⁰ and each representan alkyl group having at most 20 carbon atoms. Examples of the alkylgroup include a methyl group, an ethyl group, a propyl group, a butylgroup, a pentyl group, a hexyl group, a heptyl group, an octyl group, anonyl group, a decyl group, an undecyl group, a dodecyl group, atridecyl group, a tetradecyl group and a pentadecyl group. Furthermore,the structures of the above alkyl groups may have one or moreunsaturated bonds.

The total average content of organic substituents in a modified siliconecompound desirably falls within the range where the modified siliconecompound having an appropriate particle diameter (for example, 0.1 μm ormore and 100 μm or less) can be dispersed in a matrix, i.e., a cellulosederivative, during a process for producing a cellulose derivativecomposition. If a modified silicone compound having an appropriateparticle diameter is dispersed in a cellulose derivative, stressconcentration on the periphery of a silicone region having a low elasticmodulus effectively occurs. As a result, a resin molded body havingexcellent shock resistance can be obtained. The total average content ofsuch organic substituents is preferably 0.01% by mass or more and morepreferably 0.1% by mass or more, and also preferably 70% by mass or lessand more preferably 50% by mass or less. If an organic substituent iscontained appropriately, the modified silicone compound can be improvedin affinity for a cellulose resin, the modified silicone compound havingan appropriate particle diameter can be dispersed in a cellulosederivative, and further bleed out due to separation of the modifiedsilicone compound in a molding can be suppressed. If the total averagecontent of the organic substituents is excessively low, it becomesdifficult to disperse a modified silicone compound having an appropriateparticle diameter in a cardanol-added cellulose resin.

If an organic substituent of the modified polydimethyl siloxane compoundis an amino group, an epoxy group, a carbinol group, a phenol group, amercapto group, a carboxyl group or a methacryl group, the averagecontent of the organic substituent in the modified polydimethyl siloxanecompound can be obtained by the following Expression (I).

Organic substituent average content (%)=(organic substituentformula−weight/organic substituent equivalent)×100   (I)

In the Expression (I), the organic substituent equivalent is an averagemass of a modified silicone compound per organic substituent (1 mole).

When the organic substituent of the modified polydimethyl siloxanecompound is a phenoxy group, an alkylphenoxy group, a long-chain alkylgroup, an aralkyl group, a long-chain fatty acid ester group or along-chain fatty acid amide group, the average content of the organicsubstituent of the modified polydimethyl siloxane compound can beobtained from the following Expression (II).

Organic substituent average content (%)=x×w/[(1−x)×74+x×(59+w)]×100  (II)

In the Expression (II), x is an average molar fraction of the organicsubstituent-containing a siloxane repeat unit relative to all siloxanerepeat units of the modified polydimethyl siloxane compound; and w isthe formula weight of the organic substituent.

In the case where the organic substituent of the modified polydimethylsiloxane compound is a phenyl group, the average content of the phenylgroup in the modified polydimethyl siloxane compound can be obtained bythe following Expression (III).

Phenyl group average content (%)=154×x/[74×(1−x)+198×x]×100   (III)

In the Expression (III), x is an average molar fraction of the phenylgroup-containing siloxane repeat unit relative to all siloxane repeatunits in the modified polydimethyl siloxane compound (A).

In the case where the organic substituent of the modified polydimethylsiloxane compound is a polyether group, the average content of thepolyether group in the modified polydimethyl siloxane compound can beobtained by the following Expression (IV).

Polyether group average content (%)=HLB value/20×100   (IV)

In the Expression (IV), the HLB value represents the degree of affinityof a surfactant for water and oil, and is defined by the followingExpression (V) based on the Griffin Act.

HLB value=20×(sum of formula weights of hydrophilic moieties/molecularweight)   (V)

To the cellulose derivative of the exemplary embodiment, two or moremodified silicone compounds having different affinities to thederivative may be added. In this case, dispersibility of a relativelow-affinity modified silicone compound (A1) is improved by a relativehigh-affinity modified silicone compound (A2) to obtain a celluloseresin composition having even more excellent shock resistance. The totalaverage content of an organic substituent of the relatively low-affinitymodified silicone compound (A1) is preferably 0.01% by mass or more andmore preferably 0.1% by mass or more and also preferably 15% by mass orless and more preferably 10% by mass or less. The total average contentof an organic substituent of the relatively high-affinity modifiedsilicone compound (A2) is preferably 15% by mass or more and morepreferably 20% by mass or more and also preferably 90% by mass or less.

The blending ratio (mass ratio) of the modified silicone compound (Al)to the modified silicone compound (A2) can be set to fall within therange of 10/90 to 90/10.

In a modified silicone compound, dimethyl siloxane repeat units andorganic substituent-containing siloxane repeat units each of which maybe homologously and continuously connected, alternately connected orconnected at random. A modified silicone compound may have a branchedstructure.

The number average molecular weight of a modified silicone compound ispreferably 900 or more and more preferably 1000 or more, and alsopreferably 1000000 or less, more preferably 300000 or less and furtherpreferably 100000 or less. If the molecular weight of a modifiedsilicone compound is sufficiently large, loss by vaporization can besuppressed in kneading with a melted cellulose derivative during aprocess for producing a cellulose derivative composition. Furthermore,if the molecular weight of a modified silicone compound is appropriate(not excessively large), a uniform molding having good dispersibilitycan be obtained.

As the number average molecular weight, a value (calibrated by apolystyrene standard sample) obtained by measuring a 0.1% chloroformsolution of a sample by GPC can be employed.

The addition amount of such a modified silicone compound is preferably,in view of obtaining sufficient addition effect, 1% by mass or morerelative to the total cellulose derivative composition and morepreferably 2% by mass or more. In view of sufficiently ensuringproperties of a cellulose resin such as strength and suppressing bleedout, the addition amount of a modified silicone compound is preferably20% by mass or less and more preferably 10% by mass or less.

By adding such a modified silicone compound to a cellulose derivative,the modified silicone compound having an appropriate particle diameter(for example, 0.1 to 100 μm) can be dispersed in the resin and the shockresistance of a resin composition can be improved.

To the cellulose derivative of the exemplary embodiment, if necessary,additives such as a colorant, an antioxidant and a heat stabilizer maybe added as long as they are applied to conventional resin compositions.

To the cellulose derivative of the exemplary embodiment, if necessary, ageneral thermoplastic resin may be added.

As the thermoplastic resin, a polyester can be added and astraight-chain aliphatic polyester can be preferably used. As thestraight-chain aliphatic polyester (Y), the following straight-chainaliphatic polyesters (Y1) and (Y2) are preferable, for example,polybutylene succinate, polybutylene succinate adipate andpolycaprolactone can be mentioned.

(Y1) Straight-chain aliphatic polyester containing at least one ofrepeating units represented by the following formula (VI) and formula(VII)

—(CO—R²³—COO—R²⁴—O—)—  (VI)

—(CO—R²⁵—O—)—  (VII)

In the formula (VI), R²³ represents a divalent aliphatic group havingcarbon atoms of 1 to 12, preferably 2 to 8 and more preferably 2 to 4;and R²⁴ represents a divalent aliphatic group having carbon atoms of 2to 12, preferably 2 to 8 and more preferably 2 to 4.

In the formula (VII), R²⁵ represents a divalent aliphatic group havingcarbon atoms of 2 to 10, preferably 2 to 8 and more preferably 2 to 4.

(Y2) Straight-chain aliphatic polyester composed of a product obtainedby ring-opening polymerization of a cyclic ester.

The straight-chain aliphatic polyester (Y1) can be obtained by acondensation reaction between at least one selected from the groupconsisting of, for example, an aliphatic dicarboxylic acid, an acidanhydride thereof and a diester thereof, and an aliphatic diol.

The aliphatic dicarboxylic acid has carbon atoms of, for example, 3 to12, preferably 3 to 9, more preferably 3 to 5. The aliphatic carboxylicacid is, for example, an alkane dicarboxylic acid. Specific examplesthereof include malonic acid, succinic acid, adipic acid, sebacic acid,azelaic acid and dodecane dicarboxylic acid. The aliphatic dicarboxylicacids, for example, may be used alone or in combination of two or more.

The aliphatic diol has carbon atoms of, for example, 2 to 12, preferably2 to 8 and more preferably 2 to 6. The aliphatic diol is, for example,an alkylene glycol. Specific examples thereof include ethylene glycol,1,3-propylene glycol, 1,4-butane diol, 1,6-hexane diol, 1,9-nonane diol,1,10-decane diol and 1,12-dodecane diol. Of them, a straight-chainaliphatic diol having 2 to 6 carbon atoms is preferable, andparticularly, ethylene glycol, 1,3-propylene glycol, 1,4-butane diol and1,6-hexane diol are preferable. The aliphatic diols, for example, may beused alone or in combination of two or more.

The straight-chain aliphatic polyester (Y2) is a straight-chainaliphatic polyester obtained by ring-opening polymerization of a cyclicester. The cyclic ester is, for example, lactone having carbon atoms of2 to 12. Specific examples thereof include, α-acetolactone,β-propiolactone, γ-butyrolactone and δ-valerolactone. The cyclic esters,for example, may be used alone or in combination with two or more.

The number average molecular weight of the straight-chain aliphaticpolyester (Y) is not particularly limited. The lower limit thereof ispreferably, for example, 10000 or more, and more preferably 20000 ormore. The upper limit thereof is preferably, for example, 200000 or lessand more preferably 100000 or less. The aliphatic polyester having amolecular weight within the above range can provide, for example, a moreuniform molded body having more excellent dispersibility.

As the number average molecular weight, for example, a value (calibratedby a polystyrene standard sample) obtained by measuring a 0.1%chloroform solution of a sample by GPC can be employed.

By adding a thermoplastic resin having excellent flexibility such as athermoplastic polyurethane elastomer (TPU) to the cellulose derivativeaccording to an exemplary embodiment, shock resistance can be improved.The addition amount of such a thermoplastic resin (particularly, TPU)is, in view of obtaining sufficient addition effect, preferably 1% bymass or more and more preferably 5% by mass or more relative to thetotal composition containing the cellulose resin of the exemplaryembodiment.

The thermoplastic polyurethane elastomer (TPU) suitable for improvingshock resistance that can be used includes a polyurethane elastomerprepared by using a polyol, a diisocyanate and a chain extender.

Examples of the polyol include polyester polyol, polyester ether polyol,polycarbonate polyol and polyether polyol.

Examples of the polyester polyol include a polyester polyol obtained bya dehydration condensation reaction between a polyvalent carboxylic acidsuch as an aliphatic dicarboxylic acid (succinic acid, adipic acid,sebacic acid, azelaic acid, etc.), an aromatic dicarboxylic acid(phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc.), an alicyclic dicarboxylic acid(hexahydrophthalic acid, hexahydroterephthalic acid,hexahydroisophthalic acid, etc.), or an acid ester or an acid anhydrideof each of these, and a polyol such as ethylene glycol, 1,3-propyleneglycol, 1,2-propylene glycol, 1,3-butane diol, 1,4-butane diol,1,5-pentane diol, 1,6-hexane diol, 3-methyl-1,5-pentane diol, neopentylglycol, 1,3-octane diol, 1,9-nonane diol, or a mixture of these; and apolylactone diol obtained by ring-opening polymerization of a lactonemonomer such as ϵ-caprolactone.

Examples of the polyester ether polyol include a compound obtained by adehydration condensation reaction between a polyvalent carboxylic acidsuch as an aliphatic dicarboxylic acid (succinic acid, adipic acid,sebacic acid, azelaic acid, etc.), an aromatic dicarboxylic acid(phthalic acid, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, etc.), an alicyclic dicarboxylic acid(hexahydrophthalic acid, hexahydroterephthalic acid,hexahydroisophthalic acid, etc.), or an acid ester or an acid anhydrideof each of these, and a glycol such as diethylene glycol or an alkyleneoxide adduct (propylene oxide adduct etc.) or a mixture of these.

Examples of the polycarbonate polyol include a polycarbonate polyolobtained by reacting one or two or more polyols such as ethylene glycol,1,3-propylene glycol, 1,2-propylene glycol, 1,3-butane diol, 1,4-butanediol, 1,5-pentane diol, 1,6-hexane diol, 3-methyl-1,5-pentane diol,neopentyl glycol, 1,8-octane diol, 1,9-nonane diol and diethylene glycolwith diethylene carbonate, dimethyl carbonate, diethyl carbonate, etc.;and further may include a copolymer of a polycaprolactone polyol (PCL)and a polyhexamethylene carbonate (PHL).

Examples of the polyether polyol include a polyethylene glycol,polypropylene glycol and polytetramethylene ether glycol, each of whichis obtained by polymerizing respective cyclic ethers: ethylene oxide,propylene oxide and tetrahydrofuran; and copolyethers of these.

Examples of the diisocyanate to be used in formation of TPU includetolylene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI),1,5-naphthylene diisocyanate (NDI), tolidine diisocyanate,1,6-hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),xylylene diisocyanate (XDI), hydrogenated XDI, triisocyanate,tetramethyl xylene diisocyanate (TMXDI), 1,6,11-undecane triisocyanate,1,8-diisocyanatemethyl octane, lysine ester triisocyanate,1,3,6-hexamethylene triisocyanate, bicycloheptane triisocyanate anddicyclohexyl methane diisocyanate (hydrogenated MDI; HMDI). Of these,4,4′-diphenylmethane diisocyanate (MDI) and 1,6-hexamethylenediisocyanate (HDI) are preferably used.

Examples of the chain extender to be used in formation of TPU, alow-molecular weight polyol can be used. Examples of the low-molecularweight polyol include aliphatic polyols such as ethylene glycol,1,3-propylene glycol, 1,2-propylene glycol, 1,3-butane diol, 1,4-butanediol, 1,5-pentane diol, 1,6-hexane diol, 3-methyl-1,5-pentane diol,neopentyl glycol, 1,8-octane diol, 1,9-nonane diol, diethylene glycoland 1,4-cyclohexane dimethanol and glycerin; and aromatic glycols suchas 1,4-dimethylolbenzene, bisphenol A and ethylene oxide or a propyleneoxide adduct of bisphenol A.

When a silicone compound is copolymerized with a thermoplasticpolyurethane elastomer (TPU) obtained from these materials, furtherexcellent shock resistance can be obtained.

These thermoplastic polyurethane elastomers (TPU) may be used singly orin combination.

A method for producing a resin composition containing the cellulosederivative of the exemplary embodiment, additives and a thermoplasticresin, is not particularly limited. For example, the resin compositioncan be produced by melting and mixing additives and the cellulose resinmanually by handmixing or by use of a known mixer such as a tumblermixer, a ribbon blender, a single-axial or a multiaxial mixing extruder,and a compounding apparatus such as a kneader and kneading roll and, ifnecessary, granulating the mixture into an appropriate shape. In anotherpreferable process, additives dispersed in solvent such as an organicsolvent and a resin are mixed and furthermore, if necessary, acoagulation solvent is added to obtain a mixed composition of theadditives and the resin and thereafter, the solvent is evaporated.

The cellulose derivative according to the exemplary embodimentsmentioned above can be used as a base resin for a molding material(resin composition). The molding material using the cellulose derivativeas a base resin is suitable for forming a molded body such as housing,e.g. packaging for an electronic device.

The base resin herein refers to a main component of the molding materialand means that other components may be contained as long as thecomponents do not prevent the function of the main component. Thecontent rate of the main component is not particularly limited; however,the content rate of the main component in a composition is preferably50% by mass or more, more preferably 70% by mass or more, furtherpreferably 80% by mass or more and particularly preferably 90% by massor more.

EXAMPLES

The present invention will be more specifically described by way ofexamples below.

Synthesis Example 1 Synthesis of Raw Material of Long-Chain Reactant(Carboxylated Hydrogenated Cardanol)

Hydrogenated cardanol (m-n-pentadecylphenol manufactured by ACROSOrganics) prepared by hydrogenating an unsaturated bond of thestraight-chain hydrocarbon moiety of the cardanol was used as a rawmaterial. The phenolic hydroxy group of the hydrogenated cardanol wasreacted with monochloro acetic acid to add a carboxyl group. In thismanner, carboxylated hydrogenated cardanol was obtained. Morespecifically, carboxylated hydrogenated cardanol was prepared inaccordance with the following procedure.

First, hydrogenated cardanol (80 g (0.26 mol)) was dissolved in methanol(120 mL). To this, an aqueous solution of sodium hydroxide (64 g (1.6mol)) dissolved in distilled water (40 mL) was added. Thereafter, asolution of monochloro acetic acid (66 g (0.70 mol), manufactured byKanto Chemical Co., Inc.) dissolved in methanol (50 mL) was addeddropwise at room temperature. After completion of dropwise addition, thereaction solution was refluxed at 73° C. for 4 hours while stirring.After the reaction solution was cooled to room temperature, the reactionsolution was acidified with a diluted hydrochloric acid until pHreached 1. To this, methanol (250 mL) and diethylether (500 mL) wereadded and further distilled water (200 mL) was added. The water layerwas separated by a separation funnel and discarded. The ether layer waswashed twice with distilled water (400 mL). To the ether layer,anhydrous magnesium was added, dried, and separated by filtration. Thefiltrate (ether layer) was concentrated under vacuum by an evaporator(90° C./3 mmHg) to obtain a yellow-brown powdery crude product as asolid content. The crude product was recrystallized from n-hexane anddried under vacuum to obtain a white powder of carboxylated hydrogenatedcardanol (46 g (0.12 mol)).

Synthesis Example 2 Synthesis of a Mixture of Short-Chain and Long-ChainReactants

The carboxylated hydrogenated cardanol of Synthesis Example 1 was mixedwith an acetic anhydride and heated to obtain a mixture of the aceticanhydride, acetic acid-carboxylated hydrogenated cardanol mixed acidanhydride (asymmetric anhydride: acid anhydride formed by a dehydrationreaction between acetic acid and carboxylated hydrogenated cardanol) andacid anhydride-modified cardanol (symmetric anhydride: acid anhydrideformed by a dehydration reaction between mutual carboxylatedhydrogenated cardanol molecules). In short, a mixture of short-chain andlong-chain reactants was obtained. More specifically, the mixture ofshort-chain and long-chain reactants was prepared in accordance with thefollowing procedure.

To the carboxylated hydrogenated cardanol (40.2 g (111 mmol)) ofSynthesis Example 1, acetic anhydride (21.0 mL (222 mmol)) was added.The mixture was stirred while heating at 100° C. for one hour. In thismanner, a mixture of short-chain and long-chain reactants was obtained.

The resultant mixture of short-chain and long-chain reactants wasdissolved in deuterated chloroform and measured by ¹H-NMR (product name:AV-400, 400 MHz, manufactured by Bruker). As a result, the molar ratioof acetic anhydride: acetic acid-carboxylated hydrogenated cardanolmixed anhydride (asymmetric anhydride): acid anhydride-modified cardanol(symmetric anhydride) was 65:32:3.

Note that, the obtained acetic acid-carboxylated hydrogenated cardanolmixed acid anhydride (asymmetric anhydride) has carbon atoms of 25, theacid anhydride-modified cardanol (symmetric anhydride) has carbon atomsof 46, and the long-chain organic group (carboxylated hydrogenatedcardanol bound to a hydroxy group of cellulose via ester bond) producedin Example described later has carbon atoms of 23.

Synthesis Example 3 Synthesis of Long-Chain Reactant (Acid ChlorideModified Hydrogenated Cardanol)

The carboxylated hydrogenated cardanol synthesized in Synthesis Example1 was chlorinated with oxalyl chloride to convert a carboxyl group intoan acid chloride group to obtain acid chlorinated hydrogenated cardanol.More specifically, the acid chlorinated hydrogenated cardanol wasprepared in accordance with the following procedure.

The carboxylated hydrogenated cardanol (46 g (0.12 mol)) of SynthesisExample 1 was dissolved in dehydrated chloroform (250 mL) and oxalylchloride (24 g (0.19 mol)) and N, N-dimethylformamide (0.25 mL (3.2mmol)) were added. The mixture was stirred for 72 hours at roomtemperature. Chloroform, excessive oxalyl chloride and N,N-dimethylformamide were distillated away under reduced pressure toobtain acid chlorinated and hydrogenated cardanol (48 g (0.13 mol)).

Note that the obtained long-chain reactant (acid chloride modifiedcardanol) has 23 carbon atoms. The long-chain organic group(carboxylated hydrogenated cardanol bound to a hydroxy group of acellulose via an ester bond) to be produced in Comparative Example(described later) has 23 carbon atoms.

Reference Example 1 Reaction in Solid-Liquid Heterogeneous System(Corresponding to the First Step of Example 1

After activation treatment of a cellulose was performed, a mixture ofshort-chain and long-chain reactants of Synthesis Example 2 was reactedin a solid-liquid heterogeneous system to obtain a long-chain andshort-chain linked cellulose derivative. More specifically, thelong-chain and short-chain linked cellulose derivative was prepared inaccordance with the following procedure.

First, an activation treatment of a cellulose was performed by thefollowing method.

A cellulose (product name: KC flock, bland: W-50GK, manufactured byNIPPON PAPER INDUSTRIES Co., Ltd.) (6.0 g) (on a dry basis) wasdispersed in dimethylsulfoxide (90 mL). The dispersion solution wasstirred for 1 hour and subjected to suction filtration for 10 minutes toremove dimethylsulfoxide. In this manner, the cellulose activated wasobtained.

Next, a cellulose derivative was synthesized by the following method.

To the above cellulose activated, a dioxane solution ofdimethylaminopyridine (3.0 g) dissolved in dehydrated dioxane (150 mL)was added to obtain a dispersion solution. The dispersion solution wasadded to the mixture of short-chain and long-chain reactants ofSynthesis Example 2.

After the resultant solution was stirred while heating at 100° C. for 6hours, the reaction suspension solution was subjected to suctionfiltration to perform solid-liquid separation. The solid contentobtained as a residue was washed and dried to obtain a product (11.2 g).Washing was repeatedly performed so as not to leave an unreactedsubstance in consideration of analysis. More specifically, washing wasmade three times with 100 mL of isopropyl alcohol heated at 60° C. Thesolid content washed was dried in vacuum at 105° C. for 5 hours.

A part of the resultant solid content (long-chain and short-chain linkedcellulose derivative) was treated for analysis as follows. First, to thesolid content (0.3 g), a pyridine solution containing dimethyl aminopyridine (1.0 g) dissolved in dehydrated pyridine (20 mL) was added andfurther propionic anhydride (32 ml) was added. After the mixture wasstirred while heating at 100° C. for 3 hours, a water-methanol mixedsolution (volume ratio 1:1) (550 ml) was slowly added dropwise to makereprecipitation. The solid substance was separated by filtration. Thesolid substance obtained by reprecipitation was washed three times witha water-methanol mixed solution (volume ratio 1:1) (50 ml) and dried invacuum at 105° C. for 5 hours. In the treatment mentioned above, theremaining hydroxy groups of the solid content (long-chain andshort-chain linked cellulose derivative) were converted to propionylgroups. In this manner, the solid content was modified so as to bedissolved in deuterated chloroform.

The solid content modified was dissolved in deuterated chloroform andthe substitution degree of hydroxy groups was measured by ¹H-NMR(product name: AV-400, 400 MHz, manufactured by Bruker) to evaluate thesubstitution degree of hydroxy groups of the solid content beforemodification. As a result, the substitution degree (DS_(SH)) of thesolid content (long-chain and short-chain linked cellulose derivative)with the short-chain organic group before modification was 1.0; whereas,the substitution degree (DS_(LO)) thereof with the long-chain organicgroup was 0.3 and the hydroxy group remaining degree was 1.7.

To the filtrate obtained by solid-liquid separation, a large amount ofpoor solvent, methanol, was added for analysis. The resultantprecipitated solid substance was repeatedly washed with isopropylalcohol at 60° C. and the ratio of a cellulose derivative dissolved inthe reaction solution was calculated. As the result, the ratio was 5%.

The process chart of Reference Example 1 is shown in FIG. 1(corresponding to the first step of Example 1).

Example 1

First, an intermediate cellulose derivative was prepared in the samemanner as in Reference Example 1 (first step).

Next, to the obtained intermediate cellulose derivative (11 g), pyridine(74 ml) and acetic anhydride (86 ml) were added and stirred whileheating at 100° C. for 4 hours (second step).

Thereafter, the reaction solution was distilled away to obtain the finalcellulose derivative.

The substitution degree of hydroxy groups in the resultant solid content(long-chain and short-chain linked cellulose derivative) was measured byNMR in the same manner as in Reference Example 1. As a result, thesubstitution degree (DS_(SH)) with a short-chain organic group was 1.5,the substitution degree (DS_(LO)) with a long-chain organic group was0.3 and the hydroxy group remaining degree was 1.2. The manufacturingprocess chart of Example 1 is shown in FIG. 1.

Example 2

A long-chain and short-chain linked cellulose derivative was prepared inthe same manner as in Example 1 except that the heating time in thesecond step was set to be 18 hours. The substitution degree of hydroxygroups of the resultant solid content (long-chain and short-chain linkedcellulose derivative) was measured by NMR in the same manner as inReference Example 1. As a result, the substitution degree (DS_(SH)) witha short-chain organic group was 2.4, the substitution degree (DS_(LO))with a long-chain organic group was 0.3 and the hydroxy group remainingdegree was 0.3. The manufacturing process chart of Example 2 is shown inFIG. 1.

Example 3

First, an intermediate cellulose derivative was prepared in the samemanner as in Reference Example 1 (first step).

Next, to the obtained intermediate cellulose derivative (11 g), pyridine(74 ml), acetic anhydride (86 ml) and dimethyl amino pyridine (3.0 g)were added and stirred while heating at 100° C. for 6 hours (secondstep).

Thereafter, while stirring the reaction solution, methanol (740 mL) wasslowly added dropwise to reprecipitate a solid substance. The solidsubstance was separated by filtration. The solid content thus obtainedwas dried overnight in the air and further dried in vacuum at 105° C.for 5 hours to obtain a long-chain and short-chain linked cellulosederivative.

The substitution degree of hydroxy groups of the resultant solid content(long-chain and short-chain linked cellulose derivative) was measured byNMR in the same manner as in Reference Example 1. As a result, thesubstitution degree (DS_(SH)) with a short-chain organic group was 2.7,the substitution degree (DS_(LO)) with a long-chain organic group was0.3 and the hydroxy group remaining degree was less than 0.1.

Comparative Example 1 Reaction in Homogenous System

Acid chlorinated hydrogenated cardanol of Synthesis Example 3 andcellulose acetate (trade name: LM-80, manufactured by Daicel ChemicalIndustries, Ltd., the number of acetic acid molecules added per glucoseunit of cellulose (substitution degree by acetylation: DS_(Ace))=2.1)were reacted in a solution state. The reaction solution was added to apoor solvent to precipitate a product. In this manner, a long-chain andshort-chain linked cellulose derivative was obtained. More specifically,a long-chain and short-chain linked cellulose derivative was prepared asfollows.

Cellulose acetate (10 g) (the amount of hydroxy group: 0.036 mol) wasdissolved in dehydrated dioxane (200 mL). A triethylamine (5.0 mL (0.036mol)) serving as a reaction catalyst and an acid-trapping agent wasadded. To this solution, a dioxane solution (100 mL) dissolving the acidchlorinated hydrogenated cardanol (23 g (0.054 mol)) of SynthesisExample 3 was added and stirred while heating at 100° C. for 5 hours.The reaction solution was slowly added dropwise to methanol (3 L) whilestirring to reprecipitate a solid substance. The solid substance wasseparated by filtration. The solid content thus obtained was driedovernight in the air and further dried in vacuum at 105° C. for 5 hoursto obtain a long-chain and short-chain linked cellulose derivative (16g).

The substitution degree (DS_(LO)) of the resultant long-chain andshort-chain linked cellulose derivative with a long-chain organic groupwas measured by NMR. As a result, the substitution degree (DS_(LO)) was0.5. The manufacturing process chart of Comparative Example 1 is shownin FIG. 2.

[Evaluation of Melt Flow Rate (MFR)]

With respect to each of the cellulose derivatives of Examples 1 to 3,Reference Example 1 and Comparative Example 1, a melt flow rate servingas an index for flowability was evaluated as follows. The results aresummarized in Table 1.

After a cellulose derivative was dried at 105° C. for 7 hours, a meltflow rate (MFR) was measured by use of a measuring device (trade name:Shimadzu flow tester CFT-500D, manufactured by Shimadzu Corporation) inaccordance with JIS K7210 in the conditions: 200° C., 500 kgf/cm² (49MPa).

[Amount of Solvent]

The amounts of solvents used in producing cellulose derivatives inReference Example 1, Examples 1 to 3 and Comparative Example 1 aresummarized in Table 1. The amounts of solvents in Table 1 are shown bymass ratio (shown below). In Reference Example 1, the amount of solventused in introducing long-chain and short-chain organic groups is shownby mass ratio to the starting cellulose. In Examples 1 to 3, the totalamount of solvent used in introducing long-chain and short-chain organicgroups and solvent used in subsequent introduction of a short-chainorganic group is shown by a mass ratio to a staring cellulose. However,the amount of solvent in Example 3 includes the amount of methanol usedin reprecipitation. In Comparative Example 1, the total amount ofsolvent used in introducing a long-chain organic group and solvent usedin reprecipitation is shown by a mass ratio to the starting celluloseacetate.

TABLE 1 Compar- Reference ative Exam- Exam- Exam- Exam- Exam- ple 1 ple1 ple 2 ple 3 ple 1 Reaction Hetero- Hetero- Hetero- Hetero- Homo-system in geneous geneous geneous geneous geneous introducing a systemsystem system system system long-chain organic group Presence or AbsentPresent Present Present — absence of second step DS_(SH) 1.0 1.5 2.4 2.72.1 (short-chain) DS_(LO) 0.3 0.3 0.3 0.3 0.5 (long-chain) Hydroxy group1.7 1.2 0.3 <0.1 0.4 remaining degree Amount of 26 38 38 161 269 solvent(mass ratio to cellulose) MFR 20 490 640 40 600 (g/10 min)

As is apparent from comparison between the production steps shown inFIG. 1 and those shown in FIG. 2, as well as from Table 1, since a largeamount of poor solvent is not required in recovering a product inExamples 1, 2 and Reference Example 1, compared to Comparative Example1, the amount of solvent used is greatly low and the recovery step issimplified. Also, in Example 3, since the amount of reaction solvent inthe second step is low and the amount of solvent (poor solvent) used inreprecipitation is low, compared to Comparative Example 1, the recoveryprocess is simplified. Note that, in the second steps of Examples 1 to3, since a short-chain reactant having less steric hindrance is reacted,the degree of swelling and solubility of a cellulose derivative in areaction solution can be reduced, compared to the case where along-chain reactant having large steric hindrance is reacted. Because ofthis, the use amount of reaction solution can be reduced.

In Examples 1 to 3, since a short-chain organic group is furtherintroduced in the second step, it is found that flowability is improvedcompared to Reference Example 1. Of them, improvement of flowability issignificant particularly when the hydroxy group remaining degree is lessthan 1.7, as is in Examples 1 and 2. Particularly, in Examples 1 and 2,although the introduction amount (DS_(LO)) of a long-chain organic groupis the same as in that of Reference Example 1, flowability is improved.

Note that, the hydroxy group remaining degree is less than 0.1 inExample 3; however, flowability is low compared to Examples 1 and 2. Itcan be presumed that the ratio of a short-chain linked celluloserelatively low in flowability is high.

[Evaluation by X-Ray Diffraction]

The crystal structure of the obtained cellulose derivative was evaluatedby X-ray diffraction. As an X-ray diffractometer, X'Pert PRO (tradename) manufactured by PANalytical was used. As X-ray, CuKα beam wasused. A cellulose derivative was pressed at 200° C. and 100 kgf/cm² (9.8MPa) into a film and evaluated, or a cellulose derivative synthesizedand recovered as a solid substance is directly evaluated.

Evaluation results are shown in FIG. 3 and FIG. 4. FIG. 4 shows themeasurement results with respect to Examples 1 and 2 and ReferenceExample 1 by repeating measurement for many times particularly, in alow-angle region. In all cases, film-form samples were evaluated.

As is apparent from FIG. 3, a cellulose derivative (corresponding to thecellulose derivative obtained in the first step of Example 1) ofReference Example 1 has cellulose crystal (peak in the vicinity of2θ=22°). The symbol θ herein represents the incident angle of X-ray on ameasurement sample.

However, as is apparent form the results of Examples 1 to 3, as thenumber of short-chain organic groups to be introduced is increased,cellulose crystal disappears (FIG. 3); at the same time, crystal ofcellulose acetate is newly formed (in FIG. 4, peaks in the vicinity of2θ=8°, 10°, 13°. Note that, cellulose triacetate crystal haspolymorphisms called as CTA-I and CTA-II. It is known that CTA-I has apeak in the vicinity of 2θ=8° and CTA-II has peaks in the vicinity of2θ=8°, 10°, 13°.

Also when the cellulose derivative of Example 3, which was synthesizedand recovered as a solid substance, was directly evaluated without beingformed into a film, a peak was observed in the vicinity of 2θ=8° and thepresence of cellulose acetate crystal was confirmed.

[Degree of Swelling and Measurement Method Thereof]

Degrees of swelling of samples (cellulose derivatives) were measured asfollows.

After the length of a sample (after dried) before swollen was measuredby an optical microscope, a solvent was added dropwise to soak thesample in the solvent. In the state where the sample was soaked in thesolvent, the length of the sample was measured with time. The length ofthe sample after the swelling reached saturation was regarded as thelength of the sample after swollen and degree of swelling was calculatedin accordance with the following expression.

Degree of swelling (%)=100×(length of sample after swollen−length ofsample before swollen)/length of sample before swollen.

More specifically, first, a sample before swollen (after dried) wasplaced on a glass plate and the length (width of a fiber in this case)of the sample before swollen was measured under observation by anoptical microscope (trade name: digital microscope, model: VHX-500,manufactured by KEYENCE CORPORATION).

The length of a sample herein is determined by measuring the distancebetween two points (end points): two points at which a line passingthrough the center of the sample is crossed with the contour of thesample, in an image under observation. The shortest distance wasdetermined as the length of the sample. If the sample is fibrous form,the center of the sample corresponds to any point on the center axisalong the longitudinal direction. If the sample is spherical form, thecenter of the sample corresponds to the center of the circle (contour)in an image under observation. If the sample has a shape except fibrousform and spherical form, in an image under observation, the contour of asingle particle of the sample is surrounded by a square (a rectangularor square) having the smallest area having four corners all having anangle of 90° and the intersection of the diagonal lines of the squarecan be determined as the center of the sample. If the sample is fibrousform, the diameter (width) of the fiber correspond to the length ofsample. If the sample is spherical form, the diameter corresponds to thelength of the sample.

The degree of swelling of cellulose derivatives of Reference Example 1was determined at room temperature in accordance with the aforementionedmeasurement method. Since the sample was fibrous, the diameter (width)of the fiber was measured. Since the swelling of the sample reachedsaturation within one minute from soaking in solvent, degree of swellingwas evaluated at one minute after soaking in the solvent. Note that thelength 10 minutes after soaking in the solvent was virtually the same asthe length one minute after soaking in the solvent. The obtained resultsare shown in Table 2.

TABLE 2 Degree of swelling (%) Dioxane Methanol Long-chain and shortchain linked cellulose 25 5 derivative (Reference Example 1)

As is shown in Table 2, the long-chain and short-chain linked cellulosederivative of Reference Example 1 exhibits a high degree of swelling indioxane compared to methanol (poor solvent). As is shown in the results(Table 1) of Reference Example 1, high substitution degree is obtained.Likewise, if a reaction solution capable of attaining high degree ofswelling of a long-chain and short-chain linked cellulose derivative isused, it is probably that the cellulose derivative is sufficientlyimpregnated with a long-chain reactant and the swollen state can bemaintained until completion of the reaction, and consequently highreactivity is obtained.

Now, production of a molded body and evaluation results of the obtainedmolded body will be shown below.

Reference Example 2

Using the cellulose derivative obtained in Reference Example 1, a moldedbody was prepared by adding an additive as described as follows andphysical properties of the molded body were evaluated. As the additive,a straight-chain polyester for improving flexibility was used.

[Kneading Method]

Using a kneader (trade name: HAAKE MiniLab Rheomex CTW5, manufactured byThermo Electron Corporation), a cellulose derivative (3.75 g) andpolybutylene succinate adipate (trade name: BIONOLLE 3001MD manufacturedby Showa Denko K.K.) (3.75 g) were kneaded. At this time, thetemperature of the kneading chamber of the kneader was set at 210° C.and the rotation number was set at 60 rpm. The raw materials weresupplied from a supply port of the kneader and kneaded for 3 minutes.

[Molding Method]

Using an injection molding machine (trade name: HAAKE MiniJet II,manufactured by Thermo Electron Corporation), a molded body having thefollowing shape was prepared using the above resin composition.

The size of the molded body: thickness: 4 mm, width: 10 mm, length: 80mm

At this time, molding conditions were set as follows: the temperature ofcylinder of the molding machine: 220° C., the temperature of a mold: 60°C., injection pressure: 1200 bars (120 MPa), injection time: 5 seconds,and a pressure of 600 bar (60 MPa) was kept for 20 seconds.

[Evaluation of Compatibility]

Appearance of a molded body obtained was visually observed andcompatibility was evaluated based on the following criteria.

: transparent or semitransparent

◯: clouded (homogeneously dispersed)

×: non-homogeneously dispersed.

[Measurement of Izod Impact Strength]

Notch izod impact strength of the above molded body was measured inaccordance with JIS K7110.

Example 4

A molded body was prepared using the cellulose derivative obtained inExample 2 in the same manner as in Reference Example 2 and physicalproperties thereof were evaluated.

Example 5

A molded body was prepared using the cellulose derivative obtained inExample 3 in the same manner as in Reference Example 2 and physicalproperties thereof were evaluated.

The evaluation results of Examples 4, 5 and Reference Example 2 aresummarized in Table 3.

TABLE 3 Reference Example 4 Example 5 Example 2 Reaction system inHeterogeneous Heterogeneous Heterogeneous introducing a system systemsystem long-chain organic group Presence or absence of Present PresentAbsent second step DS_(SH) (short-chain) 2.4 2.7 1.5 DS_(LO)(long-chain) 0.3 0.3 0.3 Hydroxy group 0.3 <0.1 1.2 remaining degreeCompatibility

◯ Izod impact strength 12 72 (not broken) 3 (kJ/m²)

As is apparent from Table 3, cellulose derivatives of Examples 4 and 5have excellent compatibility with the additive compared to that ofReference Example 2. This is probably because the number of crosslinkingsites low in compatibility and derived from the hydrogen bonds ofhydroxy groups is reduced by introducing a short-chain organic group inthe second step. In addition, the impact strength of Examples 4 and 5 ishigh compared to Reference Example 2. This is because polybutylenesuccinate adipate added as a flexible component was sufficientlydissolved and thus the flexibility of the entire resin composition wasimproved.

Having thus described the present invention with reference to theexemplary embodiments and Examples, the present invention is not limitedto the above-described exemplary embodiments and Examples. Variousmodifications understandable to those skilled in the art may be made tothe constitution and details of the present invention within the scopethereof.

This application claims the right of priority based on Japanese PatentApplication No. 2013-222565 filed Oct. 25, 2013, the entire content ofwhich are incorporated herein by reference.

1. A cellulose derivative comprising a long-chain organic group having 5or more carbon atoms and at least one short-chain organic group having 4or less carbon atoms, the long-chain organic group and the short-chainorganic group being introduced therein by use of hydroxy groups of acellulose, wherein the cellulose derivative contains a crystal structurederived from a cellulose derivative portion to which the short-chainorganic group having 4 or less carbon atoms is linked, wherein thecrystal structure comprises a crystal region of the cellulose acylatedwith a short-chain acyl group having 2 to 4 carbon atoms as theshort-chain organic group, the short-chain organic group beingintroduced by use of a hydroxy group of the cellulose to form an ester,and wherein the crystal region contains only the cellulose acylated withthe short-chain acyl group.
 2. The cellulose derivative according toclaim 1, wherein an average number of hydroxy groups per glucose unit isless than 1.7.
 3. The cellulose derivative according to claim 1, whereinan average number of hydroxy groups per glucose unit is less than 1.2.4. The cellulose derivative according to claim 1, wherein an averagenumber of the short-chain organic groups introduced per glucose unit is1.3 to 2.7.
 5. The cellulose derivative according to claim 1, wherein anaverage number of the long-chain organic groups introduced per glucoseunit is 0.1 to 1.0.
 6. The cellulose derivative according to claim 1,wherein the short-chain organic group includes at least one of an acetylgroup and a propionyl group.
 7. The cellulose derivative according toclaim 1, wherein the short-chain organic group is an acetyl group. 8.The cellulose derivative according to claim 1, wherein the long-chainorganic group includes a long-chain organic group having 7 to 48 carbonatoms.
 9. The cellulose derivative according to claim 1, wherein thelong-chain organic group comprises a cardanol moiety or a hydrogenatedcardanol moiety.
 10. A cellulose derivative comprising a long-chainorganic group having 5 or more carbon atoms and at least one short-chainorganic group having 4 or less carbon atoms, the long-chain organicgroup and the short-chain organic group being introduced therein by useof hydroxy groups of a cellulose, wherein the cellulose derivativecontains a crystal structure derived from a cellulose derivative portionto which the short-chain organic group having 4 or less carbon atoms islinked, the crystal structure comprises a crystal region of thecellulose acylated with a short-chain acyl group having 2 to 4 carbonatoms as the short-chain organic group, the short-chain organic groupbeing introduced by use of a hydroxy group of the cellulose to form anester, the crystal region contains only the cellulose acylated with theshort-chain acyl group, an average number of hydroxy groups per glucoseunit is less than 1.7, an average number of the short-chain organicgroups introduced per glucose unit is 1.3 to 2.7, an average number ofthe long-chain organic groups introduced per glucose unit is 0.1 to 1.0,the short-chain organic group includes at least one of an acetyl groupand a propionyl group, and the long-chain organic group includes along-chain organic group having 7 to 48 carbon atoms, a cardanol moietyor a hydrogenated cardanol moiety.
 11. The cellulose derivativeaccording to claim 10, wherein an average number of hydroxy groups perglucose unit is less than 1.2.
 12. The cellulose derivative according toclaim 10, wherein the short-chain organic group is an acetyl group. 13.A molding resin composition comprising the cellulose derivativeaccording to claim
 1. 14. A molding resin composition comprising thecellulose derivative according to claim 10.